Updated modules.

Bumps [golang.org/x/crypto](https://github.com/golang/crypto) from 0.32.0 to 0.33.0.
- [Commits](https://github.com/golang/crypto/compare/v0.32.0...v0.33.0)

---
updated-dependencies:
- dependency-name: golang.org/x/crypto
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/actions/lfs/action.yml

@@ -1,23 +0,0 @@
-name: Git LFS pull
-description: Cached Git LFS pull.
-
-runs:
-  using: "composite"
-  steps:
-    - name: Create LFS file list
-      shell: bash
-      run: git lfs ls-files --long | cut -d ' ' -f1 | sort > .lfs-assets-id
-
-    - name: Restore LFS cache
-      uses: actions/cache@v4
-      with:
-        path: .git/lfs/objects
-        key: lfs-${{ hashFiles('.lfs-assets-id') }}
-        restore-keys: lfs-
-        enableCrossOsArchive: true
-
-    - name: Git LFS pull
-      shell: bash
-      run: |
-        git lfs pull
-        git lfs prune

.github/actions/vmactions/template.yml

@@ -0,0 +1,11 @@
+name: VM Actions matrix
+description: VM Actions matrix template
+
+runs:
+  using: composite
+  steps:
+    - uses: ${VMACTIONS}
+      with:
+        usesh: true
+        copyback: false
+        run: . ./test.sh

.github/workflows/build-test.sh

@@ -6,6 +6,10 @@ echo 'set -eu' > test.sh
 for p in $(go list ./...); do
   dir=".${p#github.com/ncruces/go-sqlite3}"
   name="$(basename "$p").test"
-  (cd ${dir}; go test -c)
-  [ -f "${dir}/${name}" ] && echo "(cd ${dir}; ./${name} ${TESTFLAGS})" >> test.sh
-done
+  (cd ${dir}; go test -c ${BUILDFLAGS:-})
+  [ -f "${dir}/${name}" ] && echo "(cd ${dir}; ./${name} ${TESTFLAGS:-})" >> test.sh
+done
+
+if [[ -v VMACTIONS ]]; then
+  envsubst < .github/actions/vmactions/template.yml > .github/actions/vmactions/action.yml
+fi

.github/workflows/cross.sh

@@ -1,27 +0,0 @@
-#!/usr/bin/env bash
-set -euo pipefail
-
-echo android       ; GOOS=android   GOARCH=amd64 go build .
-echo darwin        ; GOOS=darwin    GOARCH=amd64 go build .
-echo dragonfly     ; GOOS=dragonfly GOARCH=amd64 go build .
-echo freebsd       ; GOOS=freebsd   GOARCH=amd64 go build .
-echo illumos       ; GOOS=illumos   GOARCH=amd64 go build .
-echo ios           ; GOOS=ios       GOARCH=amd64 go build .
-echo linux         ; GOOS=linux     GOARCH=amd64 go build .
-echo netbsd        ; GOOS=netbsd    GOARCH=amd64 go build .
-echo openbsd       ; GOOS=openbsd   GOARCH=amd64 go build .
-echo plan9         ; GOOS=plan9     GOARCH=amd64 go build .
-echo solaris       ; GOOS=solaris   GOARCH=amd64 go build .
-echo windows       ; GOOS=windows   GOARCH=amd64 go build .
-echo aix           ; GOOS=aix       GOARCH=ppc64 go build .
-echo js            ; GOOS=js        GOARCH=wasm  go build .
-echo wasip1        ; GOOS=wasip1    GOARCH=wasm  go build .
-echo linux-flock   ; GOOS=linux     GOARCH=amd64 go build -tags sqlite3_flock .
-echo linux-noshm   ; GOOS=linux     GOARCH=amd64 go build -tags sqlite3_noshm .
-echo linux-nosys   ; GOOS=linux     GOARCH=amd64 go build -tags sqlite3_nosys .
-echo darwin-flock  ; GOOS=darwin    GOARCH=amd64 go build -tags sqlite3_flock .
-echo darwin-noshm  ; GOOS=darwin    GOARCH=amd64 go build -tags sqlite3_noshm .
-echo darwin-nosys  ; GOOS=darwin    GOARCH=amd64 go build -tags sqlite3_nosys .
-echo windows-nosys ; GOOS=windows   GOARCH=amd64 go build -tags sqlite3_nosys .
-echo freebsd-nosys ; GOOS=freebsd   GOARCH=amd64 go build -tags sqlite3_nosys .
-echo solaris-flock ; GOOS=solaris   GOARCH=amd64 go build -tags sqlite3_flock .

.github/workflows/cross.yml

@@ -1,16 +0,0 @@
-name: Cross compile
-
-on:
-  workflow_dispatch:
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-
-    steps:
-    - uses: actions/checkout@v4
-    - uses: actions/setup-go@v5
-      with: { go-version: stable }
-
-    - name: Build
-      run: .github/workflows/cross.sh

.github/workflows/repro.sh

@@ -2,29 +2,33 @@
 set -euo pipefail
 
 if [[ "$OSTYPE" == "linux"* ]]; then
-  WASI_SDK="https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-22/wasi-sdk-22.0-linux.tar.gz"
-  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_117/binaryen-version_117-x86_64-linux.tar.gz"
+  WASI_SDK="https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-25/wasi-sdk-25.0-x86_64-linux.tar.gz"
+  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_122/binaryen-version_122-x86_64-linux.tar.gz"
 elif [[ "$OSTYPE" == "darwin"* ]]; then
-  WASI_SDK="https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-22/wasi-sdk-22.0-macos.tar.gz"
-  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_117/binaryen-version_117-x86_64-macos.tar.gz"
+  WASI_SDK="https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-25/wasi-sdk-25.0-arm64-macos.tar.gz"
+  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_122/binaryen-version_122-arm64-macos.tar.gz"
 elif [[ "$OSTYPE" == "msys" || "$OSTYPE" == "cygwin" ]]; then
-  WASI_SDK="https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-22/wasi-sdk-22.0.m-mingw.tar.gz"
-  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_117/binaryen-version_117-x86_64-windows.tar.gz"
+  WASI_SDK="https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-25/wasi-sdk-25.0-x86_64-windows.tar.gz"
+  BINARYEN="https://github.com/WebAssembly/binaryen/releases/download/version_122/binaryen-version_122-x86_64-windows.tar.gz"
 fi
 
 # Download tools
 mkdir -p tools/
-[ -d "tools/wasi-sdk"* ]         || curl -#L "$WASI_SDK" | tar xzC tools &
-[ -d "tools/binaryen-version"* ] || curl -#L "$BINARYEN" | tar xzC tools &
+[ -d "tools/wasi-sdk" ] || curl -#L "$WASI_SDK" | tar xzC tools &
+[ -d "tools/binaryen" ] || curl -#L "$BINARYEN" | tar xzC tools &
 wait
 
+[ -d "tools/wasi-sdk" ] || mv "tools/wasi-sdk"* "tools/wasi-sdk"
+[ -d "tools/binaryen" ] || mv "tools/binaryen"* "tools/binaryen"
+
 # Download and build SQLite
 sqlite3/download.sh
 embed/build.sh
+embed/bcw2/build.sh
 
 # Download and build sqlite-createtable-parser
-util/vtabutil/parse/download.sh
-util/vtabutil/parse/build.sh
+util/sql3util/wasm/download.sh
+util/sql3util/wasm/build.sh
 
 # Check diffs
-git diff --exit-code 
+git diff --exit-code

.github/workflows/repro.yml

@@ -16,16 +16,17 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     steps:
+    - uses: ilammy/msvc-dev-cmd@v1
     - uses: actions/checkout@v4
-    - uses: actions/setup-go@v5
-      with: { go-version: stable }
 
     - name: Build
+      shell: bash
       run: .github/workflows/repro.sh
 
-    - uses: actions/attest-build-provenance@v1
+    - uses: actions/attest-build-provenance@v2
       if: matrix.os == 'ubuntu-latest'
       with:
         subject-path: |
           embed/sqlite3.wasm
-          util/vtabutil/parse/sql3parse_table.wasm
+          embed/bcw2/bcw2.wasm
+          util/sql3util/wasm/sql3parse_table.wasm

.github/workflows/test.yml

@@ -2,9 +2,19 @@ name: Test
 
 on:
   push:
-    branches: [ "main" ]
+    branches: [ 'main' ]
+    paths:
+      - '**.go'
+      - '**.mod'
+      - '**.wasm'
+      - '**.yml'
   pull_request:
-    branches: [ "main" ]
+    branches: [ 'main' ]
+    paths:
+      - '**.go'
+      - '**.mod'
+      - '**.wasm'
+      - '**.yml'
   workflow_dispatch:
 
 jobs:
@@ -19,9 +29,6 @@ jobs:
     - uses: actions/setup-go@v5
       with: { go-version: stable }
 
-    - name: Git LFS pull
-      uses: ./.github/actions/lfs
-
     - name: Format
       run: gofmt -s -w . && git diff --exit-code
       if: matrix.os != 'windows-latest'
@@ -46,69 +53,137 @@ jobs:
 
     - name: Test BSD locks
       run: go test -v -tags sqlite3_flock ./...
-      if: matrix.os == 'macos-latest'
+      if: matrix.os != 'windows-latest'
 
-    - name: Test no shared memory
-      run: go test -v -tags sqlite3_noshm ./...
-      if: matrix.os == 'ubuntu-latest'
+    - name: Test dot locks
+      run: go test -v -tags sqlite3_dotlk ./...
+      if: matrix.os != 'windows-latest'
 
-    - name: Test no locks
-      run: go test -v -tags sqlite3_nosys ./...
-      if: matrix.os == 'ubuntu-latest'
+    - name: Test modules
+      shell: bash
+      run: |
+        go work init .
+        go work use -r embed gormlite
+        go test -v ./embed/bcw2/...
 
     - name: Test GORM
+      shell: bash
       run: gormlite/test.sh
+      if: matrix.os != 'windows-latest'
+
+    - name: Collect coverage
+      run: |
+        go get -tool github.com/dave/courtney@v0.4.4
+        go tool courtney
+      if: |
+        github.event_name == 'push' &&
+        matrix.os == 'ubuntu-latest'
 
     - uses: ncruces/go-coverage-report@v0
       with:
+        coverage-file: coverage.out
         chart: true
         amend: true
       if: |
         github.event_name == 'push' &&
         matrix.os == 'ubuntu-latest'
 
-  test-intel:
-    runs-on: macos-13
-    needs: test
-
-    steps:
-    - uses: actions/checkout@v4
-    - uses: actions/setup-go@v5
-      with: { go-version: stable }
-
-    - name: Git LFS pull
-      uses: ./.github/actions/lfs
-
-    - name: Test
-      run: go test -v ./...
-
   test-bsd:
+    strategy:
+      matrix:
+        os:
+          - name: freebsd
+            version: '14.2'
+            flags: '-test.v'
+          - name: netbsd
+            version: '10.1'
+            flags: '-test.v'
+          - name: freebsd
+            arch: arm64
+            version: '14.2'
+            flags: '-test.v -test.short'
+          - name: netbsd
+            arch: arm64
+            version: '10.1'
+            flags: '-test.v -test.short'
+          - name: openbsd
+            version: '7.6'
+            flags: '-test.v -test.short'
     runs-on: ubuntu-latest
     needs: test
 
     steps:
     - uses: actions/checkout@v4
-    - uses: actions/setup-go@v5
-      with: { go-version: stable }
-
-    - name: Git LFS pull
-      uses: ./.github/actions/lfs
 
     - name: Build
       env:
-        GOOS: freebsd
-        TESTFLAGS: '-test.v'
+        GOOS: ${{ matrix.os.name }}
+        GOARCH: ${{ matrix.os.arch }}
+        TESTFLAGS: ${{ matrix.os.flags }}
       run: .github/workflows/build-test.sh
 
     - name: Test
-      uses: cross-platform-actions/action@v0.24.0
+      uses: cross-platform-actions/action@v0.27.0
       with:
-        operating_system: freebsd
-        version: '14.0'
+        operating_system: ${{ matrix.os.name }}
+        architecture: ${{ matrix.os.arch }}
+        version: ${{ matrix.os.version }}
         shell: bash
         run: . ./test.sh
         sync_files: runner-to-vm
 
+  test-vm:
+    strategy:
+      matrix:
+        os:
+          - name: dragonfly
+            action: 'vmactions/dragonflybsd-vm@v1'
+            tflags: '-test.v'
+          - name: illumos
+            action: 'vmactions/omnios-vm@v1'
+            tflags: '-test.v'
+          - name: solaris
+            action: 'vmactions/solaris-vm@v1'
+            bflags: '-tags sqlite3_dotlk'
+            tflags: '-test.v'
+    runs-on: ubuntu-latest
+    needs: test
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Build
+      env:
+        GOOS: ${{ matrix.os.name }}
+        BUILDFLAGS: ${{ matrix.os.bflags }}
+        TESTFLAGS:  ${{ matrix.os.tflags }}
+        VMACTIONS:  ${{ matrix.os.action }}
+      run: .github/workflows/build-test.sh
+
+    - name: Test
+      uses: ./.github/actions/vmactions
+
+  test-wasip1:
+    runs-on: ubuntu-latest
+    needs: test
+
+    steps:
+    - uses: bytecodealliance/actions/wasmtime/setup@v1
+    - uses: actions/checkout@v4
+    - uses: actions/setup-go@v5
+      with: { go-version: stable }
+
+    - name: Set path
+      run: echo "$(go env GOROOT)/lib/wasm" >> "$GITHUB_PATH"
+
+    - name: Test wasmtime
+      env:
+        GOOS: wasip1
+        GOARCH: wasm
+        GOWASIRUNTIME: wasmtime
+        GOWASIRUNTIMEARGS: '--env CI=true'
+      run: go test -v -short -tags sqlite3_dotlk -skip Example ./...
+
   test-qemu:
     runs-on: ubuntu-latest
     needs: test
@@ -119,23 +194,20 @@ jobs:
     - uses: actions/setup-go@v5
       with: { go-version: stable }
 
-    - name: Git LFS pull
-      uses: ./.github/actions/lfs
-
     - name: Test 386 (32-bit)
       run: GOARCH=386 go test -v -short ./...
 
-    - name: Test arm64 (compiler)
-      run: GOARCH=arm64 go test -v -short ./...
-
     - name: Test riscv64 (interpreter)
       run: GOARCH=riscv64 go test -v -short ./...
 
-    - name: Test s390x (big-endian, z/OS demo)
-      run: GOARCH=s390x go test -v -short -tags sqlite3_flock ./...
+    - name: Test ppc64le (interpreter)
+      run: GOARCH=ppc64le go test -v -short ./...
 
-  test-vm:
-    runs-on: ubuntu-latest
+    - name: Test s390x (big-endian)
+      run: GOARCH=s390x go test -v -short -tags sqlite3_dotlk ./...
+
+  test-linuxarm:
+    runs-on: ubuntu-24.04-arm
     needs: test
 
     steps:
@@ -143,32 +215,17 @@ jobs:
     - uses: actions/setup-go@v5
       with: { go-version: stable }
 
-    - name: Git LFS pull
-      uses: ./.github/actions/lfs
+    - name: Test
+      run: go test -v ./...
 
-    - name: Build illumos
-      env:
-        GOOS: illumos
-        TESTFLAGS: '-test.v -test.short'
-      run: .github/workflows/build-test.sh
+  test-macintel:
+    runs-on: macos-13
+    needs: test
 
-    - name: Test illumos
-      uses: vmactions/omnios-vm@v1
-      with:
-        usesh: true
-        copyback: false
-        run: . ./test.sh
+    steps:
+    - uses: actions/checkout@v4
+    - uses: actions/setup-go@v5
+      with: { go-version: stable }
 
-    - name: Build Solaris
-      env:
-        GOOS: solaris
-        TESTFLAGS: '-test.v -test.short'
-      run: .github/workflows/build-test.sh
-
-    - name: Test Solaris
-      uses: vmactions/solaris-vm@v1
-      with:
-        usesh: true
-        copyback: false
-        run: . ./test.sh
-      continue-on-error: true
+    - name: Test
+      run: go test -v ./...

.gitignore

@@ -13,4 +13,11 @@
 
 # Dependency directories (remove the comment below to include it)
 # vendor/
-tools
+tools
+
+# Go workspace file
+go.work
+go.work.sum
+
+# env file
+.env

README.md

@@ -1,4 +1,4 @@
-# Go bindings to SQLite using Wazero
+# Go bindings to SQLite using wazero
 
 [![Go Reference](https://pkg.go.dev/badge/image)](https://pkg.go.dev/github.com/ncruces/go-sqlite3)
 [![Go Report](https://goreportcard.com/badge/github.com/ncruces/go-sqlite3)](https://goreportcard.com/report/github.com/ncruces/go-sqlite3)
@@ -10,7 +10,21 @@ as well as direct access to most of the [C SQLite API](https://sqlite.org/cintro
 
 It wraps a [Wasm](https://webassembly.org/) [build](embed/) of SQLite,
 and uses [wazero](https://wazero.io/) as the runtime.\
-Go, wazero and [`x/sys`](https://pkg.go.dev/golang.org/x/sys) are the _only_ runtime dependencies [^1].
+Go, wazero and [`x/sys`](https://pkg.go.dev/golang.org/x/sys) are the _only_ direct dependencies.
+
+### Getting started
+
+Using the [`database/sql`](https://pkg.go.dev/database/sql) driver:
+```go
+
+import "database/sql"
+import _ "github.com/ncruces/go-sqlite3/driver"
+import _ "github.com/ncruces/go-sqlite3/embed"
+
+var version string
+db, _ := sql.Open("sqlite3", "file:demo.db")
+db.QueryRow(`SELECT sqlite_version()`).Scan(&version)
+```
 
 ### Packages
 
@@ -27,39 +41,6 @@ Go, wazero and [`x/sys`](https://pkg.go.dev/golang.org/x/sys) are the _only_ run
 - [`github.com/ncruces/go-sqlite3/gormlite`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/gormlite)
   provides a [GORM](https://gorm.io) driver.
 
-### Extensions
-
-- [`github.com/ncruces/go-sqlite3/ext/array`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/array)
-  provides the [`array`](https://sqlite.org/carray.html) table-valued function.
-- [`github.com/ncruces/go-sqlite3/ext/blobio`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/blobio)
-  simplifies [incremental BLOB I/O](https://sqlite.org/c3ref/blob_open.html).
-- [`github.com/ncruces/go-sqlite3/ext/bloom`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/bloom)
-  provides a [Bloom filter](https://github.com/nalgeon/sqlean/issues/27#issuecomment-1002267134) virtual table.
-- [`github.com/ncruces/go-sqlite3/ext/csv`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/csv)
-  reads [comma-separated values](https://sqlite.org/csv.html).
-- [`github.com/ncruces/go-sqlite3/ext/fileio`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/fileio)
-  reads, writes and lists files.
-- [`github.com/ncruces/go-sqlite3/ext/hash`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/hash)
-  provides cryptographic hash functions.
-- [`github.com/ncruces/go-sqlite3/ext/lines`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/lines)
-  reads data [line-by-line](https://github.com/asg017/sqlite-lines).
-- [`github.com/ncruces/go-sqlite3/ext/pivot`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/pivot)
-  creates [pivot tables](https://github.com/jakethaw/pivot_vtab).
-- [`github.com/ncruces/go-sqlite3/ext/statement`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/statement)
-  creates [parameterized views](https://github.com/0x09/sqlite-statement-vtab).
-- [`github.com/ncruces/go-sqlite3/ext/stats`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/stats)
-  provides [statistics](https://www.oreilly.com/library/view/sql-in-a/9780596155322/ch04s02.html) functions.
-- [`github.com/ncruces/go-sqlite3/ext/unicode`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/unicode)
-  provides [Unicode aware](https://sqlite.org/src/dir/ext/icu) functions.
-- [`github.com/ncruces/go-sqlite3/ext/zorder`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/zorder)
-  maps multidimensional data to one dimension.
-- [`github.com/ncruces/go-sqlite3/vfs/adiantum`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/vfs/adiantum)
-  wraps a VFS to offer encryption at rest.
-- [`github.com/ncruces/go-sqlite3/vfs/memdb`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/vfs/memdb)
-  implements an in-memory VFS.
-- [`github.com/ncruces/go-sqlite3/vfs/readervfs`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/vfs/readervfs)
-  implements a VFS for immutable databases.
-
 ### Advanced features
 
 - [incremental BLOB I/O](https://sqlite.org/c3ref/blob_open.html)
@@ -72,7 +53,11 @@ Go, wazero and [`x/sys`](https://pkg.go.dev/golang.org/x/sys) are the _only_ run
 - [math functions](https://sqlite.org/lang_mathfunc.html)
 - [full-text search](https://sqlite.org/fts5.html)
 - [geospatial search](https://sqlite.org/geopoly.html)
+- [Unicode support](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/unicode)
+- [statistics functions](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/stats)
 - [encryption at rest](vfs/adiantum/README.md)
+- [many extensions](ext/README.md)
+- [custom VFSes](vfs/README.md#custom-vfses)
 - [and more…](embed/README.md)
 
 ### Caveats
@@ -89,9 +74,10 @@ This project aims for [high test coverage](https://github.com/ncruces/go-sqlite3
 It also benefits greatly from [SQLite's](https://sqlite.org/testing.html) and
 [wazero's](https://tetrate.io/blog/introducing-wazero-from-tetrate/#:~:text=Rock%2Dsolid%20test%20approach) thorough testing.
 
-Every commit is [tested](.github/workflows/test.yml) on
-Linux (amd64/arm64/386/riscv64/s390x), macOS (amd64/arm64),
-Windows (amd64), FreeBSD (amd64), illumos (amd64), and Solaris (amd64).
+Every commit is [tested](https://github.com/ncruces/go-sqlite3/wiki/Support-matrix) on
+Linux (amd64/arm64/386/riscv64/ppc64le/s390x), macOS (amd64/arm64),
+Windows (amd64), FreeBSD (amd64/arm64), OpenBSD (amd64), NetBSD (amd64/arm64),
+DragonFly BSD (amd64), illumos (amd64), and Solaris (amd64).
 
 The Go VFS is tested by running SQLite's
 [mptest](https://github.com/sqlite/sqlite/blob/master/mptest/mptest.c).
@@ -104,12 +90,20 @@ Perfomance of the [`database/sql`](https://pkg.go.dev/database/sql) driver is
 The Wasm and VFS layers are also tested by running SQLite's
 [speedtest1](https://github.com/sqlite/sqlite/blob/master/test/speedtest1.c).
 
+### FAQ, issues, new features
+
+For questions, please see [Discussions](https://github.com/ncruces/go-sqlite3/discussions/categories/q-a).
+
+Also, post there if you used this driver for something interesting
+([_"Show and tell"_](https://github.com/ncruces/go-sqlite3/discussions/categories/show-and-tell)),
+have an [idea](https://github.com/ncruces/go-sqlite3/discussions/categories/ideas)…
+
+The [Issue](https://github.com/ncruces/go-sqlite3/issues) tracker is for bugs we want fixed,
+and features we're working on, planning to work on, or asking for help with.
+
 ### Alternatives
 
 - [`modernc.org/sqlite`](https://pkg.go.dev/modernc.org/sqlite)
 - [`crawshaw.io/sqlite`](https://pkg.go.dev/crawshaw.io/sqlite)
 - [`github.com/mattn/go-sqlite3`](https://pkg.go.dev/github.com/mattn/go-sqlite3)
 - [`github.com/zombiezen/go-sqlite`](https://pkg.go.dev/github.com/zombiezen/go-sqlite)
-
-[^1]: anything else you find in `go.mod` is either a test dependency,
-      or needed by one of the extensions.

backup.go

@@ -5,8 +5,8 @@ package sqlite3
 // https://sqlite.org/c3ref/backup.html
 type Backup struct {
 	c      *Conn
-	handle uint32
-	otherc uint32
+	handle ptr_t
+	otherc ptr_t
 }
 
 // Backup backs up srcDB on the src connection to the "main" database in dstURI.
@@ -61,7 +61,7 @@ func (src *Conn) BackupInit(srcDB, dstURI string) (*Backup, error) {
 	return src.backupInit(dst, "main", src.handle, srcDB)
 }
 
-func (c *Conn) backupInit(dst uint32, dstName string, src uint32, srcName string) (*Backup, error) {
+func (c *Conn) backupInit(dst ptr_t, dstName string, src ptr_t, srcName string) (*Backup, error) {
 	defer c.arena.mark()()
 	dstPtr := c.arena.string(dstName)
 	srcPtr := c.arena.string(srcName)
@@ -71,19 +71,19 @@ func (c *Conn) backupInit(dst uint32, dstName string, src uint32, srcName string
 		other = src
 	}
 
-	r := c.call("sqlite3_backup_init",
-		uint64(dst), uint64(dstPtr),
-		uint64(src), uint64(srcPtr))
-	if r == 0 {
+	ptr := ptr_t(c.call("sqlite3_backup_init",
+		stk_t(dst), stk_t(dstPtr),
+		stk_t(src), stk_t(srcPtr)))
+	if ptr == 0 {
 		defer c.closeDB(other)
-		r = c.call("sqlite3_errcode", uint64(dst))
-		return nil, c.sqlite.error(r, dst)
+		rc := res_t(c.call("sqlite3_errcode", stk_t(dst)))
+		return nil, c.sqlite.error(rc, dst)
 	}
 
 	return &Backup{
 		c:      c,
 		otherc: other,
-		handle: uint32(r),
+		handle: ptr,
 	}, nil
 }
 
@@ -97,10 +97,10 @@ func (b *Backup) Close() error {
 		return nil
 	}
 
-	r := b.c.call("sqlite3_backup_finish", uint64(b.handle))
+	rc := res_t(b.c.call("sqlite3_backup_finish", stk_t(b.handle)))
 	b.c.closeDB(b.otherc)
 	b.handle = 0
-	return b.c.error(r)
+	return b.c.error(rc)
 }
 
 // Step copies up to nPage pages between the source and destination databases.
@@ -108,11 +108,11 @@ func (b *Backup) Close() error {
 //
 // https://sqlite.org/c3ref/backup_finish.html#sqlite3backupstep
 func (b *Backup) Step(nPage int) (done bool, err error) {
-	r := b.c.call("sqlite3_backup_step", uint64(b.handle), uint64(nPage))
-	if r == _DONE {
+	rc := res_t(b.c.call("sqlite3_backup_step", stk_t(b.handle), stk_t(nPage)))
+	if rc == _DONE {
 		return true, nil
 	}
-	return false, b.c.error(r)
+	return false, b.c.error(rc)
 }
 
 // Remaining returns the number of pages still to be backed up
@@ -120,8 +120,8 @@ func (b *Backup) Step(nPage int) (done bool, err error) {
 //
 // https://sqlite.org/c3ref/backup_finish.html#sqlite3backupremaining
 func (b *Backup) Remaining() int {
-	r := b.c.call("sqlite3_backup_remaining", uint64(b.handle))
-	return int(int32(r))
+	n := int32(b.c.call("sqlite3_backup_remaining", stk_t(b.handle)))
+	return int(n)
 }
 
 // PageCount returns the total number of pages in the source database
@@ -129,6 +129,6 @@ func (b *Backup) Remaining() int {
 //
 // https://sqlite.org/c3ref/backup_finish.html#sqlite3backuppagecount
 func (b *Backup) PageCount() int {
-	r := b.c.call("sqlite3_backup_pagecount", uint64(b.handle))
-	return int(int32(r))
+	n := int32(b.c.call("sqlite3_backup_pagecount", stk_t(b.handle)))
+	return int(n)
 }

blob.go

@@ -20,7 +20,9 @@ type Blob struct {
 	c      *Conn
 	bytes  int64
 	offset int64
-	handle uint32
+	handle ptr_t
+	bufptr ptr_t
+	buflen int64
 }
 
 var _ io.ReadWriteSeeker = &Blob{}
@@ -29,29 +31,29 @@ var _ io.ReadWriteSeeker = &Blob{}
 //
 // https://sqlite.org/c3ref/blob_open.html
 func (c *Conn) OpenBlob(db, table, column string, row int64, write bool) (*Blob, error) {
-	c.checkInterrupt()
 	defer c.arena.mark()()
 	blobPtr := c.arena.new(ptrlen)
 	dbPtr := c.arena.string(db)
 	tablePtr := c.arena.string(table)
 	columnPtr := c.arena.string(column)
 
-	var flags uint64
+	var flags int32
 	if write {
 		flags = 1
 	}
 
-	r := c.call("sqlite3_blob_open", uint64(c.handle),
-		uint64(dbPtr), uint64(tablePtr), uint64(columnPtr),
-		uint64(row), flags, uint64(blobPtr))
+	c.checkInterrupt(c.handle)
+	rc := res_t(c.call("sqlite3_blob_open", stk_t(c.handle),
+		stk_t(dbPtr), stk_t(tablePtr), stk_t(columnPtr),
+		stk_t(row), stk_t(flags), stk_t(blobPtr)))
 
-	if err := c.error(r); err != nil {
+	if err := c.error(rc); err != nil {
 		return nil, err
 	}
 
 	blob := Blob{c: c}
-	blob.handle = util.ReadUint32(c.mod, blobPtr)
-	blob.bytes = int64(c.call("sqlite3_blob_bytes", uint64(blob.handle)))
+	blob.handle = util.Read32[ptr_t](c.mod, blobPtr)
+	blob.bytes = int64(int32(c.call("sqlite3_blob_bytes", stk_t(blob.handle))))
 	return &blob, nil
 }
 
@@ -65,10 +67,10 @@ func (b *Blob) Close() error {
 		return nil
 	}
 
-	r := b.c.call("sqlite3_blob_close", uint64(b.handle))
-
+	rc := res_t(b.c.call("sqlite3_blob_close", stk_t(b.handle)))
+	b.c.free(b.bufptr)
 	b.handle = 0
-	return b.c.error(r)
+	return b.c.error(rc)
 }
 
 // Size returns the size of the BLOB in bytes.
@@ -86,18 +88,19 @@ func (b *Blob) Read(p []byte) (n int, err error) {
 		return 0, io.EOF
 	}
 
-	avail := b.bytes - b.offset
 	want := int64(len(p))
+	avail := b.bytes - b.offset
 	if want > avail {
 		want = avail
 	}
+	if want > b.buflen {
+		b.bufptr = b.c.realloc(b.bufptr, want)
+		b.buflen = want
+	}
 
-	defer b.c.arena.mark()()
-	ptr := b.c.arena.new(uint64(want))
-
-	r := b.c.call("sqlite3_blob_read", uint64(b.handle),
-		uint64(ptr), uint64(want), uint64(b.offset))
-	err = b.c.error(r)
+	rc := res_t(b.c.call("sqlite3_blob_read", stk_t(b.handle),
+		stk_t(b.bufptr), stk_t(want), stk_t(b.offset)))
+	err = b.c.error(rc)
 	if err != nil {
 		return 0, err
 	}
@@ -106,7 +109,7 @@ func (b *Blob) Read(p []byte) (n int, err error) {
 		err = io.EOF
 	}
 
-	copy(p, util.View(b.c.mod, ptr, uint64(want)))
+	copy(p, util.View(b.c.mod, b.bufptr, want))
 	return int(want), err
 }
 
@@ -123,19 +126,20 @@ func (b *Blob) WriteTo(w io.Writer) (n int64, err error) {
 	if want > avail {
 		want = avail
 	}
-
-	defer b.c.arena.mark()()
-	ptr := b.c.arena.new(uint64(want))
+	if want > b.buflen {
+		b.bufptr = b.c.realloc(b.bufptr, want)
+		b.buflen = want
+	}
 
 	for want > 0 {
-		r := b.c.call("sqlite3_blob_read", uint64(b.handle),
-			uint64(ptr), uint64(want), uint64(b.offset))
-		err = b.c.error(r)
+		rc := res_t(b.c.call("sqlite3_blob_read", stk_t(b.handle),
+			stk_t(b.bufptr), stk_t(want), stk_t(b.offset)))
+		err = b.c.error(rc)
 		if err != nil {
 			return n, err
 		}
 
-		mem := util.View(b.c.mod, ptr, uint64(want))
+		mem := util.View(b.c.mod, b.bufptr, want)
 		m, err := w.Write(mem[:want])
 		b.offset += int64(m)
 		n += int64(m)
@@ -143,6 +147,7 @@ func (b *Blob) WriteTo(w io.Writer) (n int64, err error) {
 			return n, err
 		}
 		if int64(m) != want {
+			// notest // Write misbehaving
 			return n, io.ErrShortWrite
 		}
 
@@ -158,12 +163,16 @@ func (b *Blob) WriteTo(w io.Writer) (n int64, err error) {
 //
 // https://sqlite.org/c3ref/blob_write.html
 func (b *Blob) Write(p []byte) (n int, err error) {
-	defer b.c.arena.mark()()
-	ptr := b.c.arena.bytes(p)
+	want := int64(len(p))
+	if want > b.buflen {
+		b.bufptr = b.c.realloc(b.bufptr, want)
+		b.buflen = want
+	}
+	util.WriteBytes(b.c.mod, b.bufptr, p)
 
-	r := b.c.call("sqlite3_blob_write", uint64(b.handle),
-		uint64(ptr), uint64(len(p)), uint64(b.offset))
-	err = b.c.error(r)
+	rc := res_t(b.c.call("sqlite3_blob_write", stk_t(b.handle),
+		stk_t(b.bufptr), stk_t(want), stk_t(b.offset)))
+	err = b.c.error(rc)
 	if err != nil {
 		return 0, err
 	}
@@ -186,17 +195,18 @@ func (b *Blob) ReadFrom(r io.Reader) (n int64, err error) {
 	if want < 1 {
 		want = 1
 	}
-
-	defer b.c.arena.mark()()
-	ptr := b.c.arena.new(uint64(want))
+	if want > b.buflen {
+		b.bufptr = b.c.realloc(b.bufptr, want)
+		b.buflen = want
+	}
 
 	for {
-		mem := util.View(b.c.mod, ptr, uint64(want))
+		mem := util.View(b.c.mod, b.bufptr, want)
 		m, err := r.Read(mem[:want])
 		if m > 0 {
-			r := b.c.call("sqlite3_blob_write", uint64(b.handle),
-				uint64(ptr), uint64(m), uint64(b.offset))
-			err := b.c.error(r)
+			rc := res_t(b.c.call("sqlite3_blob_write", stk_t(b.handle),
+				stk_t(b.bufptr), stk_t(m), stk_t(b.offset)))
+			err := b.c.error(rc)
 			if err != nil {
 				return n, err
 			}
@@ -243,8 +253,9 @@ func (b *Blob) Seek(offset int64, whence int) (int64, error) {
 //
 // https://sqlite.org/c3ref/blob_reopen.html
 func (b *Blob) Reopen(row int64) error {
-	err := b.c.error(b.c.call("sqlite3_blob_reopen", uint64(b.handle), uint64(row)))
-	b.bytes = int64(b.c.call("sqlite3_blob_bytes", uint64(b.handle)))
+	b.c.checkInterrupt(b.c.handle)
+	err := b.c.error(res_t(b.c.call("sqlite3_blob_reopen", stk_t(b.handle), stk_t(row))))
+	b.bytes = int64(int32(b.c.call("sqlite3_blob_bytes", stk_t(b.handle))))
 	b.offset = 0
 	return err
 }

config.go

@@ -2,9 +2,13 @@ package sqlite3
 
 import (
 	"context"
+	"fmt"
+	"strconv"
+
+	"github.com/tetratelabs/wazero/api"
 
 	"github.com/ncruces/go-sqlite3/internal/util"
-	"github.com/tetratelabs/wazero/api"
+	"github.com/ncruces/go-sqlite3/vfs"
 )
 
 // Config makes configuration changes to a database connection.
@@ -14,10 +18,21 @@ import (
 //
 // https://sqlite.org/c3ref/db_config.html
 func (c *Conn) Config(op DBConfig, arg ...bool) (bool, error) {
-	defer c.arena.mark()()
-	argsPtr := c.arena.new(2 * ptrlen)
+	if op < DBCONFIG_ENABLE_FKEY || op > DBCONFIG_REVERSE_SCANORDER {
+		return false, MISUSE
+	}
 
-	var flag int
+	// We need to call sqlite3_db_config, a variadic function.
+	// We only support the `int int*` variants.
+	// The int is a three-valued bool: -1 queries, 0/1 sets false/true.
+	// The int* points to where new state will be written to.
+	// The vararg is a pointer to an array containing these arguments:
+	// an int and an int* pointing to that int.
+
+	defer c.arena.mark()()
+	argsPtr := c.arena.new(intlen + ptrlen)
+
+	var flag int32
 	switch {
 	case len(arg) == 0:
 		flag = -1
@@ -25,56 +40,162 @@ func (c *Conn) Config(op DBConfig, arg ...bool) (bool, error) {
 		flag = 1
 	}
 
-	util.WriteUint32(c.mod, argsPtr+0*ptrlen, uint32(flag))
-	util.WriteUint32(c.mod, argsPtr+1*ptrlen, argsPtr)
+	util.Write32(c.mod, argsPtr+0*ptrlen, flag)
+	util.Write32(c.mod, argsPtr+1*ptrlen, argsPtr)
 
-	r := c.call("sqlite3_db_config", uint64(c.handle),
-		uint64(op), uint64(argsPtr))
-	return util.ReadUint32(c.mod, argsPtr) != 0, c.error(r)
+	rc := res_t(c.call("sqlite3_db_config", stk_t(c.handle),
+		stk_t(op), stk_t(argsPtr)))
+	return util.ReadBool(c.mod, argsPtr), c.error(rc)
 }
 
 // ConfigLog sets up the error logging callback for the connection.
 //
 // https://sqlite.org/errlog.html
 func (c *Conn) ConfigLog(cb func(code ExtendedErrorCode, msg string)) error {
-	var enable uint64
+	var enable int32
 	if cb != nil {
 		enable = 1
 	}
-	r := c.call("sqlite3_config_log_go", enable)
-	if err := c.error(r); err != nil {
+	rc := res_t(c.call("sqlite3_config_log_go", stk_t(enable)))
+	if err := c.error(rc); err != nil {
 		return err
 	}
 	c.log = cb
 	return nil
 }
 
-func logCallback(ctx context.Context, mod api.Module, _, iCode, zMsg uint32) {
+func logCallback(ctx context.Context, mod api.Module, _ ptr_t, iCode res_t, zMsg ptr_t) {
 	if c, ok := ctx.Value(connKey{}).(*Conn); ok && c.log != nil {
 		msg := util.ReadString(mod, zMsg, _MAX_LENGTH)
 		c.log(xErrorCode(iCode), msg)
 	}
 }
 
+// Log writes a message into the error log established by [Conn.ConfigLog].
+//
+// https://sqlite.org/c3ref/log.html
+func (c *Conn) Log(code ExtendedErrorCode, format string, a ...any) {
+	if c.log != nil {
+		c.log(code, fmt.Sprintf(format, a...))
+	}
+}
+
+// FileControl allows low-level control of database files.
+// Only a subset of opcodes are supported.
+//
+// https://sqlite.org/c3ref/file_control.html
+func (c *Conn) FileControl(schema string, op FcntlOpcode, arg ...any) (any, error) {
+	defer c.arena.mark()()
+	ptr := c.arena.new(max(ptrlen, intlen))
+
+	var schemaPtr ptr_t
+	if schema != "" {
+		schemaPtr = c.arena.string(schema)
+	}
+
+	var rc res_t
+	var ret any
+	switch op {
+	default:
+		return nil, MISUSE
+
+	case FCNTL_RESET_CACHE:
+		rc = res_t(c.call("sqlite3_file_control",
+			stk_t(c.handle), stk_t(schemaPtr),
+			stk_t(op), 0))
+
+	case FCNTL_PERSIST_WAL, FCNTL_POWERSAFE_OVERWRITE:
+		var flag int32
+		switch {
+		case len(arg) == 0:
+			flag = -1
+		case arg[0]:
+			flag = 1
+		}
+		util.Write32(c.mod, ptr, flag)
+		rc = res_t(c.call("sqlite3_file_control",
+			stk_t(c.handle), stk_t(schemaPtr),
+			stk_t(op), stk_t(ptr)))
+		ret = util.ReadBool(c.mod, ptr)
+
+	case FCNTL_CHUNK_SIZE:
+		util.Write32(c.mod, ptr, int32(arg[0].(int)))
+		rc = res_t(c.call("sqlite3_file_control",
+			stk_t(c.handle), stk_t(schemaPtr),
+			stk_t(op), stk_t(ptr)))
+
+	case FCNTL_RESERVE_BYTES:
+		bytes := -1
+		if len(arg) > 0 {
+			bytes = arg[0].(int)
+		}
+		util.Write32(c.mod, ptr, int32(bytes))
+		rc = res_t(c.call("sqlite3_file_control",
+			stk_t(c.handle), stk_t(schemaPtr),
+			stk_t(op), stk_t(ptr)))
+		ret = int(util.Read32[int32](c.mod, ptr))
+
+	case FCNTL_DATA_VERSION:
+		rc = res_t(c.call("sqlite3_file_control",
+			stk_t(c.handle), stk_t(schemaPtr),
+			stk_t(op), stk_t(ptr)))
+		ret = util.Read32[uint32](c.mod, ptr)
+
+	case FCNTL_LOCKSTATE:
+		rc = res_t(c.call("sqlite3_file_control",
+			stk_t(c.handle), stk_t(schemaPtr),
+			stk_t(op), stk_t(ptr)))
+		ret = util.Read32[vfs.LockLevel](c.mod, ptr)
+
+	case FCNTL_VFS_POINTER:
+		rc = res_t(c.call("sqlite3_file_control",
+			stk_t(c.handle), stk_t(schemaPtr),
+			stk_t(op), stk_t(ptr)))
+		if rc == _OK {
+			const zNameOffset = 16
+			ptr = util.Read32[ptr_t](c.mod, ptr)
+			ptr = util.Read32[ptr_t](c.mod, ptr+zNameOffset)
+			name := util.ReadString(c.mod, ptr, _MAX_NAME)
+			ret = vfs.Find(name)
+		}
+
+	case FCNTL_FILE_POINTER, FCNTL_JOURNAL_POINTER:
+		rc = res_t(c.call("sqlite3_file_control",
+			stk_t(c.handle), stk_t(schemaPtr),
+			stk_t(op), stk_t(ptr)))
+		if rc == _OK {
+			const fileHandleOffset = 4
+			ptr = util.Read32[ptr_t](c.mod, ptr)
+			ptr = util.Read32[ptr_t](c.mod, ptr+fileHandleOffset)
+			ret = util.GetHandle(c.ctx, ptr)
+		}
+	}
+
+	if err := c.error(rc); err != nil {
+		return nil, err
+	}
+	return ret, nil
+}
+
 // Limit allows the size of various constructs to be
 // limited on a connection by connection basis.
 //
 // https://sqlite.org/c3ref/limit.html
 func (c *Conn) Limit(id LimitCategory, value int) int {
-	r := c.call("sqlite3_limit", uint64(c.handle), uint64(id), uint64(value))
-	return int(int32(r))
+	v := int32(c.call("sqlite3_limit", stk_t(c.handle), stk_t(id), stk_t(value)))
+	return int(v)
 }
 
 // SetAuthorizer registers an authorizer callback with the database connection.
 //
 // https://sqlite.org/c3ref/set_authorizer.html
-func (c *Conn) SetAuthorizer(cb func(action AuthorizerActionCode, name3rd, name4th, schema, nameInner string) AuthorizerReturnCode) error {
-	var enable uint64
+func (c *Conn) SetAuthorizer(cb func(action AuthorizerActionCode, name3rd, name4th, schema, inner string) AuthorizerReturnCode) error {
+	var enable int32
 	if cb != nil {
 		enable = 1
 	}
-	r := c.call("sqlite3_set_authorizer_go", uint64(c.handle), enable)
-	if err := c.error(r); err != nil {
+	rc := res_t(c.call("sqlite3_set_authorizer_go", stk_t(c.handle), stk_t(enable)))
+	if err := c.error(rc); err != nil {
 		return err
 	}
 	c.authorizer = cb
@@ -82,9 +203,9 @@ func (c *Conn) SetAuthorizer(cb func(action AuthorizerActionCode, name3rd, name4
 
 }
 
-func authorizerCallback(ctx context.Context, mod api.Module, pDB uint32, action AuthorizerActionCode, zName3rd, zName4th, zSchema, zNameInner uint32) (rc AuthorizerReturnCode) {
+func authorizerCallback(ctx context.Context, mod api.Module, pDB ptr_t, action AuthorizerActionCode, zName3rd, zName4th, zSchema, zInner ptr_t) (rc AuthorizerReturnCode) {
 	if c, ok := ctx.Value(connKey{}).(*Conn); ok && c.handle == pDB && c.authorizer != nil {
-		var name3rd, name4th, schema, nameInner string
+		var name3rd, name4th, schema, inner string
 		if zName3rd != 0 {
 			name3rd = util.ReadString(mod, zName3rd, _MAX_NAME)
 		}
@@ -94,52 +215,90 @@ func authorizerCallback(ctx context.Context, mod api.Module, pDB uint32, action
 		if zSchema != 0 {
 			schema = util.ReadString(mod, zSchema, _MAX_NAME)
 		}
-		if zNameInner != 0 {
-			nameInner = util.ReadString(mod, zNameInner, _MAX_NAME)
+		if zInner != 0 {
+			inner = util.ReadString(mod, zInner, _MAX_NAME)
 		}
-		rc = c.authorizer(action, name3rd, name4th, schema, nameInner)
+		rc = c.authorizer(action, name3rd, name4th, schema, inner)
 	}
 	return rc
 }
 
-// WalCheckpoint checkpoints a WAL database.
+// Trace registers a trace callback function against the database connection.
+//
+// https://sqlite.org/c3ref/trace_v2.html
+func (c *Conn) Trace(mask TraceEvent, cb func(evt TraceEvent, arg1 any, arg2 any) error) error {
+	rc := res_t(c.call("sqlite3_trace_go", stk_t(c.handle), stk_t(mask)))
+	if err := c.error(rc); err != nil {
+		return err
+	}
+	c.trace = cb
+	return nil
+}
+
+func traceCallback(ctx context.Context, mod api.Module, evt TraceEvent, pDB, pArg1, pArg2 ptr_t) (rc res_t) {
+	if c, ok := ctx.Value(connKey{}).(*Conn); ok && c.handle == pDB && c.trace != nil {
+		var arg1, arg2 any
+		if evt == TRACE_CLOSE {
+			arg1 = c
+		} else {
+			for _, s := range c.stmts {
+				if pArg1 == s.handle {
+					arg1 = s
+					switch evt {
+					case TRACE_STMT:
+						arg2 = s.SQL()
+					case TRACE_PROFILE:
+						arg2 = util.Read64[int64](mod, pArg2)
+					}
+					break
+				}
+			}
+		}
+		if arg1 != nil {
+			_, rc = errorCode(c.trace(evt, arg1, arg2), ERROR)
+		}
+	}
+	return rc
+}
+
+// WALCheckpoint checkpoints a WAL database.
 //
 // https://sqlite.org/c3ref/wal_checkpoint_v2.html
-func (c *Conn) WalCheckpoint(schema string, mode CheckpointMode) (nLog, nCkpt int, err error) {
+func (c *Conn) WALCheckpoint(schema string, mode CheckpointMode) (nLog, nCkpt int, err error) {
 	defer c.arena.mark()()
 	nLogPtr := c.arena.new(ptrlen)
 	nCkptPtr := c.arena.new(ptrlen)
 	schemaPtr := c.arena.string(schema)
-	r := c.call("sqlite3_wal_checkpoint_v2",
-		uint64(c.handle), uint64(schemaPtr), uint64(mode),
-		uint64(nLogPtr), uint64(nCkptPtr))
-	nLog = int(int32(util.ReadUint32(c.mod, nLogPtr)))
-	nCkpt = int(int32(util.ReadUint32(c.mod, nCkptPtr)))
-	return nLog, nCkpt, c.error(r)
+	rc := res_t(c.call("sqlite3_wal_checkpoint_v2",
+		stk_t(c.handle), stk_t(schemaPtr), stk_t(mode),
+		stk_t(nLogPtr), stk_t(nCkptPtr)))
+	nLog = int(util.Read32[int32](c.mod, nLogPtr))
+	nCkpt = int(util.Read32[int32](c.mod, nCkptPtr))
+	return nLog, nCkpt, c.error(rc)
 }
 
-// WalAutoCheckpoint configures WAL auto-checkpoints.
+// WALAutoCheckpoint configures WAL auto-checkpoints.
 //
 // https://sqlite.org/c3ref/wal_autocheckpoint.html
-func (c *Conn) WalAutoCheckpoint(pages int) error {
-	r := c.call("sqlite3_wal_autocheckpoint", uint64(c.handle), uint64(pages))
-	return c.error(r)
+func (c *Conn) WALAutoCheckpoint(pages int) error {
+	rc := res_t(c.call("sqlite3_wal_autocheckpoint", stk_t(c.handle), stk_t(pages)))
+	return c.error(rc)
 }
 
-// WalHook registers a callback function to be invoked
+// WALHook registers a callback function to be invoked
 // each time data is committed to a database in WAL mode.
 //
 // https://sqlite.org/c3ref/wal_hook.html
-func (c *Conn) WalHook(cb func(db *Conn, schema string, pages int) error) {
-	var enable uint64
+func (c *Conn) WALHook(cb func(db *Conn, schema string, pages int) error) {
+	var enable int32
 	if cb != nil {
 		enable = 1
 	}
-	c.call("sqlite3_wal_hook_go", uint64(c.handle), enable)
+	c.call("sqlite3_wal_hook_go", stk_t(c.handle), stk_t(enable))
 	c.wal = cb
 }
 
-func walCallback(ctx context.Context, mod api.Module, _, pDB, zSchema uint32, pages int32) (rc uint32) {
+func walCallback(ctx context.Context, mod api.Module, _, pDB, zSchema ptr_t, pages int32) (rc res_t) {
 	if c, ok := ctx.Value(connKey{}).(*Conn); ok && c.handle == pDB && c.wal != nil {
 		schema := util.ReadString(mod, zSchema, _MAX_NAME)
 		err := c.wal(c, schema, int(pages))
@@ -152,13 +311,73 @@ func walCallback(ctx context.Context, mod api.Module, _, pDB, zSchema uint32, pa
 //
 // https://sqlite.org/c3ref/autovacuum_pages.html
 func (c *Conn) AutoVacuumPages(cb func(schema string, dbPages, freePages, bytesPerPage uint) uint) error {
-	funcPtr := util.AddHandle(c.ctx, cb)
-	r := c.call("sqlite3_autovacuum_pages_go", uint64(c.handle), uint64(funcPtr))
-	return c.error(r)
+	var funcPtr ptr_t
+	if cb != nil {
+		funcPtr = util.AddHandle(c.ctx, cb)
+	}
+	rc := res_t(c.call("sqlite3_autovacuum_pages_go", stk_t(c.handle), stk_t(funcPtr)))
+	return c.error(rc)
 }
 
-func autoVacuumCallback(ctx context.Context, mod api.Module, pApp, zSchema, nDbPage, nFreePage, nBytePerPage uint32) uint32 {
+func autoVacuumCallback(ctx context.Context, mod api.Module, pApp, zSchema ptr_t, nDbPage, nFreePage, nBytePerPage uint32) uint32 {
 	fn := util.GetHandle(ctx, pApp).(func(schema string, dbPages, freePages, bytesPerPage uint) uint)
 	schema := util.ReadString(mod, zSchema, _MAX_NAME)
 	return uint32(fn(schema, uint(nDbPage), uint(nFreePage), uint(nBytePerPage)))
 }
+
+// SoftHeapLimit imposes a soft limit on heap size.
+//
+// https://sqlite.org/c3ref/hard_heap_limit64.html
+func (c *Conn) SoftHeapLimit(n int64) int64 {
+	return int64(c.call("sqlite3_soft_heap_limit64", stk_t(n)))
+}
+
+// HardHeapLimit imposes a hard limit on heap size.
+//
+// https://sqlite.org/c3ref/hard_heap_limit64.html
+func (c *Conn) HardHeapLimit(n int64) int64 {
+	return int64(c.call("sqlite3_hard_heap_limit64", stk_t(n)))
+}
+
+// EnableChecksums enables checksums on a database.
+//
+// https://sqlite.org/cksumvfs.html
+func (c *Conn) EnableChecksums(schema string) error {
+	r, err := c.FileControl(schema, FCNTL_RESERVE_BYTES)
+	if err != nil {
+		return err
+	}
+	if r == 8 {
+		// Correct value, enabled.
+		return nil
+	}
+	if r == 0 {
+		// Default value, enable.
+		_, err = c.FileControl(schema, FCNTL_RESERVE_BYTES, 8)
+		if err != nil {
+			return err
+		}
+		r, err = c.FileControl(schema, FCNTL_RESERVE_BYTES)
+		if err != nil {
+			return err
+		}
+	}
+	if r != 8 {
+		// Invalid value.
+		return util.ErrorString("sqlite3: reserve bytes must be 8, is: " + strconv.Itoa(r.(int)))
+	}
+
+	// VACUUM the database.
+	if schema != "" {
+		err = c.Exec(`VACUUM ` + QuoteIdentifier(schema))
+	} else {
+		err = c.Exec(`VACUUM`)
+	}
+	if err != nil {
+		return err
+	}
+
+	// Checkpoint the WAL.
+	_, _, err = c.WALCheckpoint(schema, CHECKPOINT_RESTART)
+	return err
+}

conn.go

@@ -4,13 +4,16 @@ import (
 	"context"
 	"fmt"
 	"math"
+	"math/rand"
 	"net/url"
+	"runtime"
 	"strings"
 	"time"
 
+	"github.com/tetratelabs/wazero/api"
+
 	"github.com/ncruces/go-sqlite3/internal/util"
 	"github.com/ncruces/go-sqlite3/vfs"
-	"github.com/tetratelabs/wazero/api"
 )
 
 // Conn is a database connection handle.
@@ -22,27 +25,37 @@ type Conn struct {
 
 	interrupt  context.Context
 	pending    *Stmt
-	busy       func(int) bool
+	stmts      []*Stmt
+	busy       func(context.Context, int) bool
 	log        func(xErrorCode, string)
 	collation  func(*Conn, string)
+	wal        func(*Conn, string, int) error
+	trace      func(TraceEvent, any, any) error
 	authorizer func(AuthorizerActionCode, string, string, string, string) AuthorizerReturnCode
 	update     func(AuthorizerActionCode, string, string, int64)
 	commit     func() bool
 	rollback   func()
-	wal        func(*Conn, string, int) error
-	arena      arena
 
-	handle uint32
+	busy1st time.Time
+	busylst time.Time
+	arena   arena
+	handle  ptr_t
 }
 
-// Open calls [OpenFlags] with [OPEN_READWRITE], [OPEN_CREATE], [OPEN_URI] and [OPEN_NOFOLLOW].
+// Open calls [OpenFlags] with [OPEN_READWRITE], [OPEN_CREATE] and [OPEN_URI].
 func Open(filename string) (*Conn, error) {
-	return newConn(filename, OPEN_READWRITE|OPEN_CREATE|OPEN_URI|OPEN_NOFOLLOW)
+	return newConn(context.Background(), filename, OPEN_READWRITE|OPEN_CREATE|OPEN_URI)
+}
+
+// OpenContext is like [Open] but includes a context,
+// which is used to interrupt the process of opening the connectiton.
+func OpenContext(ctx context.Context, filename string) (*Conn, error) {
+	return newConn(ctx, filename, OPEN_READWRITE|OPEN_CREATE|OPEN_URI)
 }
 
 // OpenFlags opens an SQLite database file as specified by the filename argument.
 //
-// If none of the required flags is used, a combination of [OPEN_READWRITE] and [OPEN_CREATE] is used.
+// If none of the required flags are used, a combination of [OPEN_READWRITE] and [OPEN_CREATE] is used.
 // If a URI filename is used, PRAGMA statements to execute can be specified using "_pragma":
 //
 //	sqlite3.Open("file:demo.db?_pragma=busy_timeout(10000)")
@@ -52,46 +65,58 @@ func OpenFlags(filename string, flags OpenFlag) (*Conn, error) {
 	if flags&(OPEN_READONLY|OPEN_READWRITE|OPEN_CREATE) == 0 {
 		flags |= OPEN_READWRITE | OPEN_CREATE
 	}
-	return newConn(filename, flags)
+	return newConn(context.Background(), filename, flags)
 }
 
-type connKey struct{}
+type connKey = util.ConnKey
 
-func newConn(filename string, flags OpenFlag) (conn *Conn, err error) {
-	sqlite, err := instantiateSQLite()
+func newConn(ctx context.Context, filename string, flags OpenFlag) (ret *Conn, _ error) {
+	err := ctx.Err()
+	if err != nil {
+		return nil, err
+	}
+
+	c := &Conn{interrupt: ctx}
+	c.sqlite, err = instantiateSQLite()
 	if err != nil {
 		return nil, err
 	}
 	defer func() {
-		if conn == nil {
-			sqlite.close()
+		if ret == nil {
+			c.Close()
+			c.sqlite.close()
+		} else {
+			c.interrupt = context.Background()
 		}
 	}()
 
-	c := &Conn{sqlite: sqlite}
-	c.arena = c.newArena(1024)
 	c.ctx = context.WithValue(c.ctx, connKey{}, c)
+	c.arena = c.newArena()
 	c.handle, err = c.openDB(filename, flags)
+	if err == nil {
+		err = initExtensions(c)
+	}
 	if err != nil {
 		return nil, err
 	}
 	return c, nil
 }
 
-func (c *Conn) openDB(filename string, flags OpenFlag) (uint32, error) {
+func (c *Conn) openDB(filename string, flags OpenFlag) (ptr_t, error) {
 	defer c.arena.mark()()
 	connPtr := c.arena.new(ptrlen)
 	namePtr := c.arena.string(filename)
 
 	flags |= OPEN_EXRESCODE
-	r := c.call("sqlite3_open_v2", uint64(namePtr), uint64(connPtr), uint64(flags), 0)
+	rc := res_t(c.call("sqlite3_open_v2", stk_t(namePtr), stk_t(connPtr), stk_t(flags), 0))
 
-	handle := util.ReadUint32(c.mod, connPtr)
-	if err := c.sqlite.error(r, handle); err != nil {
+	handle := util.Read32[ptr_t](c.mod, connPtr)
+	if err := c.sqlite.error(rc, handle); err != nil {
 		c.closeDB(handle)
 		return 0, err
 	}
 
+	c.call("sqlite3_progress_handler_go", stk_t(handle), 100)
 	if flags|OPEN_URI != 0 && strings.HasPrefix(filename, "file:") {
 		var pragmas strings.Builder
 		if _, after, ok := strings.Cut(filename, "?"); ok {
@@ -103,22 +128,22 @@ func (c *Conn) openDB(filename string, flags OpenFlag) (uint32, error) {
 			}
 		}
 		if pragmas.Len() != 0 {
+			c.checkInterrupt(handle)
 			pragmaPtr := c.arena.string(pragmas.String())
-			r := c.call("sqlite3_exec", uint64(handle), uint64(pragmaPtr), 0, 0, 0)
-			if err := c.sqlite.error(r, handle, pragmas.String()); err != nil {
+			rc := res_t(c.call("sqlite3_exec", stk_t(handle), stk_t(pragmaPtr), 0, 0, 0))
+			if err := c.sqlite.error(rc, handle, pragmas.String()); err != nil {
 				err = fmt.Errorf("sqlite3: invalid _pragma: %w", err)
 				c.closeDB(handle)
 				return 0, err
 			}
 		}
 	}
-	c.call("sqlite3_progress_handler_go", uint64(handle), 100)
 	return handle, nil
 }
 
-func (c *Conn) closeDB(handle uint32) {
-	r := c.call("sqlite3_close_v2", uint64(handle))
-	if err := c.sqlite.error(r, handle); err != nil {
+func (c *Conn) closeDB(handle ptr_t) {
+	rc := res_t(c.call("sqlite3_close_v2", stk_t(handle)))
+	if err := c.sqlite.error(rc, handle); err != nil {
 		panic(err)
 	}
 }
@@ -140,8 +165,8 @@ func (c *Conn) Close() error {
 	c.pending.Close()
 	c.pending = nil
 
-	r := c.call("sqlite3_close", uint64(c.handle))
-	if err := c.error(r); err != nil {
+	rc := res_t(c.call("sqlite3_close", stk_t(c.handle)))
+	if err := c.error(rc); err != nil {
 		return err
 	}
 
@@ -154,12 +179,12 @@ func (c *Conn) Close() error {
 //
 // https://sqlite.org/c3ref/exec.html
 func (c *Conn) Exec(sql string) error {
-	c.checkInterrupt()
 	defer c.arena.mark()()
 	sqlPtr := c.arena.string(sql)
 
-	r := c.call("sqlite3_exec", uint64(c.handle), uint64(sqlPtr), 0, 0, 0)
-	return c.error(r, sql)
+	c.checkInterrupt(c.handle)
+	rc := res_t(c.call("sqlite3_exec", stk_t(c.handle), stk_t(sqlPtr), 0, 0, 0))
+	return c.error(rc, sql)
 }
 
 // Prepare calls [Conn.PrepareFlags] with no flags.
@@ -183,22 +208,24 @@ func (c *Conn) PrepareFlags(sql string, flags PrepareFlag) (stmt *Stmt, tail str
 	tailPtr := c.arena.new(ptrlen)
 	sqlPtr := c.arena.string(sql)
 
-	r := c.call("sqlite3_prepare_v3", uint64(c.handle),
-		uint64(sqlPtr), uint64(len(sql)+1), uint64(flags),
-		uint64(stmtPtr), uint64(tailPtr))
+	c.checkInterrupt(c.handle)
+	rc := res_t(c.call("sqlite3_prepare_v3", stk_t(c.handle),
+		stk_t(sqlPtr), stk_t(len(sql)+1), stk_t(flags),
+		stk_t(stmtPtr), stk_t(tailPtr)))
 
 	stmt = &Stmt{c: c}
-	stmt.handle = util.ReadUint32(c.mod, stmtPtr)
-	if sql := sql[util.ReadUint32(c.mod, tailPtr)-sqlPtr:]; sql != "" {
+	stmt.handle = util.Read32[ptr_t](c.mod, stmtPtr)
+	if sql := sql[util.Read32[ptr_t](c.mod, tailPtr)-sqlPtr:]; sql != "" {
 		tail = sql
 	}
 
-	if err := c.error(r, sql); err != nil {
+	if err := c.error(rc, sql); err != nil {
 		return nil, "", err
 	}
 	if stmt.handle == 0 {
 		return nil, "", nil
 	}
+	c.stmts = append(c.stmts, stmt)
 	return stmt, tail, nil
 }
 
@@ -206,9 +233,7 @@ func (c *Conn) PrepareFlags(sql string, flags PrepareFlag) (stmt *Stmt, tail str
 //
 // https://sqlite.org/c3ref/db_name.html
 func (c *Conn) DBName(n int) string {
-	r := c.call("sqlite3_db_name", uint64(c.handle), uint64(n))
-
-	ptr := uint32(r)
+	ptr := ptr_t(c.call("sqlite3_db_name", stk_t(c.handle), stk_t(n)))
 	if ptr == 0 {
 		return ""
 	}
@@ -219,35 +244,34 @@ func (c *Conn) DBName(n int) string {
 //
 // https://sqlite.org/c3ref/db_filename.html
 func (c *Conn) Filename(schema string) *vfs.Filename {
-	var ptr uint32
+	var ptr ptr_t
 	if schema != "" {
 		defer c.arena.mark()()
 		ptr = c.arena.string(schema)
 	}
-
-	r := c.call("sqlite3_db_filename", uint64(c.handle), uint64(ptr))
-	return vfs.OpenFilename(c.ctx, c.mod, uint32(r), vfs.OPEN_MAIN_DB)
+	ptr = ptr_t(c.call("sqlite3_db_filename", stk_t(c.handle), stk_t(ptr)))
+	return vfs.GetFilename(c.ctx, c.mod, ptr, vfs.OPEN_MAIN_DB)
 }
 
 // ReadOnly determines if a database is read-only.
 //
 // https://sqlite.org/c3ref/db_readonly.html
 func (c *Conn) ReadOnly(schema string) (ro bool, ok bool) {
-	var ptr uint32
+	var ptr ptr_t
 	if schema != "" {
 		defer c.arena.mark()()
 		ptr = c.arena.string(schema)
 	}
-	r := c.call("sqlite3_db_readonly", uint64(c.handle), uint64(ptr))
-	return int32(r) > 0, int32(r) < 0
+	b := int32(c.call("sqlite3_db_readonly", stk_t(c.handle), stk_t(ptr)))
+	return b > 0, b < 0
 }
 
 // GetAutocommit tests the connection for auto-commit mode.
 //
 // https://sqlite.org/c3ref/get_autocommit.html
 func (c *Conn) GetAutocommit() bool {
-	r := c.call("sqlite3_get_autocommit", uint64(c.handle))
-	return r != 0
+	b := int32(c.call("sqlite3_get_autocommit", stk_t(c.handle)))
+	return b != 0
 }
 
 // LastInsertRowID returns the rowid of the most recent successful INSERT
@@ -255,8 +279,7 @@ func (c *Conn) GetAutocommit() bool {
 //
 // https://sqlite.org/c3ref/last_insert_rowid.html
 func (c *Conn) LastInsertRowID() int64 {
-	r := c.call("sqlite3_last_insert_rowid", uint64(c.handle))
-	return int64(r)
+	return int64(c.call("sqlite3_last_insert_rowid", stk_t(c.handle)))
 }
 
 // SetLastInsertRowID allows the application to set the value returned by
@@ -264,7 +287,7 @@ func (c *Conn) LastInsertRowID() int64 {
 //
 // https://sqlite.org/c3ref/set_last_insert_rowid.html
 func (c *Conn) SetLastInsertRowID(id int64) {
-	c.call("sqlite3_set_last_insert_rowid", uint64(c.handle), uint64(id))
+	c.call("sqlite3_set_last_insert_rowid", stk_t(c.handle), stk_t(id))
 }
 
 // Changes returns the number of rows modified, inserted or deleted
@@ -273,8 +296,7 @@ func (c *Conn) SetLastInsertRowID(id int64) {
 //
 // https://sqlite.org/c3ref/changes.html
 func (c *Conn) Changes() int64 {
-	r := c.call("sqlite3_changes64", uint64(c.handle))
-	return int64(r)
+	return int64(c.call("sqlite3_changes64", stk_t(c.handle)))
 }
 
 // TotalChanges returns the number of rows modified, inserted or deleted
@@ -283,20 +305,18 @@ func (c *Conn) Changes() int64 {
 //
 // https://sqlite.org/c3ref/total_changes.html
 func (c *Conn) TotalChanges() int64 {
-	r := c.call("sqlite3_total_changes64", uint64(c.handle))
-	return int64(r)
+	return int64(c.call("sqlite3_total_changes64", stk_t(c.handle)))
 }
 
 // ReleaseMemory frees memory used by a database connection.
 //
 // https://sqlite.org/c3ref/db_release_memory.html
 func (c *Conn) ReleaseMemory() error {
-	r := c.call("sqlite3_db_release_memory", uint64(c.handle))
-	return c.error(r)
+	rc := res_t(c.call("sqlite3_db_release_memory", stk_t(c.handle)))
+	return c.error(rc)
 }
 
-// GetInterrupt gets the context set with [Conn.SetInterrupt],
-// or nil if none was set.
+// GetInterrupt gets the context set with [Conn.SetInterrupt].
 func (c *Conn) GetInterrupt() context.Context {
 	return c.interrupt
 }
@@ -316,39 +336,48 @@ func (c *Conn) GetInterrupt() context.Context {
 //
 // https://sqlite.org/c3ref/interrupt.html
 func (c *Conn) SetInterrupt(ctx context.Context) (old context.Context) {
-	// Is it the same context?
-	if ctx == c.interrupt {
-		return ctx
+	old = c.interrupt
+	c.interrupt = ctx
+
+	if ctx == old || ctx.Done() == old.Done() {
+		return old
 	}
 
 	// A busy SQL statement prevents SQLite from ignoring an interrupt
 	// that comes before any other statements are started.
 	if c.pending == nil {
-		c.pending, _, _ = c.Prepare(`WITH RECURSIVE c(x) AS (VALUES(0) UNION ALL SELECT x FROM c) SELECT x FROM c`)
+		defer c.arena.mark()()
+		stmtPtr := c.arena.new(ptrlen)
+		loopPtr := c.arena.string(`WITH RECURSIVE c(x) AS (VALUES(0) UNION ALL SELECT x FROM c) SELECT x FROM c`)
+		c.call("sqlite3_prepare_v3", stk_t(c.handle), stk_t(loopPtr), math.MaxUint64,
+			stk_t(PREPARE_PERSISTENT), stk_t(stmtPtr), 0)
+		c.pending = &Stmt{c: c}
+		c.pending.handle = util.Read32[ptr_t](c.mod, stmtPtr)
 	}
 
-	old = c.interrupt
-	c.interrupt = ctx
-
-	if old != nil && old.Done() != nil && (ctx == nil || ctx.Err() == nil) {
+	if old.Done() != nil && ctx.Err() == nil {
 		c.pending.Reset()
 	}
-	if ctx != nil && ctx.Done() != nil {
+	if ctx.Done() != nil {
 		c.pending.Step()
 	}
 	return old
 }
 
-func (c *Conn) checkInterrupt() {
-	if c.interrupt != nil && c.interrupt.Err() != nil {
-		c.call("sqlite3_interrupt", uint64(c.handle))
+func (c *Conn) checkInterrupt(handle ptr_t) {
+	if c.interrupt.Err() != nil {
+		c.call("sqlite3_interrupt", stk_t(handle))
 	}
 }
 
-func progressCallback(ctx context.Context, mod api.Module, pDB uint32) (interrupt uint32) {
-	if c, ok := ctx.Value(connKey{}).(*Conn); ok && c.handle == pDB &&
-		c.interrupt != nil && c.interrupt.Err() != nil {
-		interrupt = 1
+func progressCallback(ctx context.Context, mod api.Module, _ ptr_t) (interrupt int32) {
+	if c, ok := ctx.Value(connKey{}).(*Conn); ok {
+		if c.interrupt.Done() != nil {
+			runtime.Gosched()
+		}
+		if c.interrupt.Err() != nil {
+			interrupt = 1
+		}
 	}
 	return interrupt
 }
@@ -358,69 +387,126 @@ func progressCallback(ctx context.Context, mod api.Module, pDB uint32) (interrup
 // https://sqlite.org/c3ref/busy_timeout.html
 func (c *Conn) BusyTimeout(timeout time.Duration) error {
 	ms := min((timeout+time.Millisecond-1)/time.Millisecond, math.MaxInt32)
-	r := c.call("sqlite3_busy_timeout", uint64(c.handle), uint64(ms))
-	return c.error(r)
+	rc := res_t(c.call("sqlite3_busy_timeout", stk_t(c.handle), stk_t(ms)))
+	return c.error(rc)
 }
 
-func timeoutCallback(ctx context.Context, mod api.Module, pDB uint32, count, tmout int32) (retry uint32) {
-	if c, ok := ctx.Value(connKey{}).(*Conn); ok &&
-		(c.interrupt == nil || c.interrupt.Err() == nil) {
-		const delays = "\x01\x02\x05\x0a\x0f\x14\x19\x19\x19\x32\x32\x64"
-		const totals = "\x00\x01\x03\x08\x12\x21\x35\x4e\x67\x80\xb2\xe4"
-		const ndelay = int32(len(delays) - 1)
-
-		var delay, prior int32
-		if count <= ndelay {
-			delay = int32(delays[count])
-			prior = int32(totals[count])
-		} else {
-			delay = int32(delays[ndelay])
-			prior = int32(totals[ndelay]) + delay*(count-ndelay)
+func timeoutCallback(ctx context.Context, mod api.Module, count, tmout int32) (retry int32) {
+	// https://fractaledmind.github.io/2024/04/15/sqlite-on-rails-the-how-and-why-of-optimal-performance/
+	if c, ok := ctx.Value(connKey{}).(*Conn); ok && c.interrupt.Err() == nil {
+		switch {
+		case count == 0:
+			c.busy1st = time.Now()
+		case time.Since(c.busy1st) >= time.Duration(tmout)*time.Millisecond:
+			return 0
 		}
-
-		if delay = min(delay, tmout-prior); delay > 0 {
-			time.Sleep(time.Duration(delay) * time.Millisecond)
-			retry = 1
+		if time.Since(c.busylst) < time.Millisecond {
+			const sleepIncrement = 2*1024*1024 - 1 // power of two, ~2ms
+			time.Sleep(time.Duration(rand.Int63() & sleepIncrement))
 		}
+		c.busylst = time.Now()
+		return 1
 	}
-	return retry
+	return 0
 }
 
 // BusyHandler registers a callback to handle [BUSY] errors.
 //
 // https://sqlite.org/c3ref/busy_handler.html
-func (c *Conn) BusyHandler(cb func(count int) (retry bool)) error {
-	var enable uint64
+func (c *Conn) BusyHandler(cb func(ctx context.Context, count int) (retry bool)) error {
+	var enable int32
 	if cb != nil {
 		enable = 1
 	}
-	r := c.call("sqlite3_busy_handler_go", uint64(c.handle), enable)
-	if err := c.error(r); err != nil {
+	rc := res_t(c.call("sqlite3_busy_handler_go", stk_t(c.handle), stk_t(enable)))
+	if err := c.error(rc); err != nil {
 		return err
 	}
 	c.busy = cb
 	return nil
 }
 
-func busyCallback(ctx context.Context, mod api.Module, pDB uint32, count int32) (retry uint32) {
-	if c, ok := ctx.Value(connKey{}).(*Conn); ok && c.handle == pDB && c.busy != nil &&
-		(c.interrupt == nil || c.interrupt.Err() == nil) {
-		if c.busy(int(count)) {
+func busyCallback(ctx context.Context, mod api.Module, pDB ptr_t, count int32) (retry int32) {
+	if c, ok := ctx.Value(connKey{}).(*Conn); ok && c.handle == pDB && c.busy != nil {
+		interrupt := c.interrupt
+		if interrupt == nil {
+			interrupt = context.Background()
+		}
+		if interrupt.Err() == nil && c.busy(interrupt, int(count)) {
 			retry = 1
 		}
 	}
 	return retry
 }
 
-func (c *Conn) error(rc uint64, sql ...string) error {
+// Status retrieves runtime status information about a database connection.
+//
+// https://sqlite.org/c3ref/db_status.html
+func (c *Conn) Status(op DBStatus, reset bool) (current, highwater int, err error) {
+	defer c.arena.mark()()
+	hiPtr := c.arena.new(intlen)
+	curPtr := c.arena.new(intlen)
+
+	var i int32
+	if reset {
+		i = 1
+	}
+
+	rc := res_t(c.call("sqlite3_db_status", stk_t(c.handle),
+		stk_t(op), stk_t(curPtr), stk_t(hiPtr), stk_t(i)))
+	if err = c.error(rc); err == nil {
+		current = int(util.Read32[int32](c.mod, curPtr))
+		highwater = int(util.Read32[int32](c.mod, hiPtr))
+	}
+	return
+}
+
+// TableColumnMetadata extracts metadata about a column of a table.
+//
+// https://sqlite.org/c3ref/table_column_metadata.html
+func (c *Conn) TableColumnMetadata(schema, table, column string) (declType, collSeq string, notNull, primaryKey, autoInc bool, err error) {
+	defer c.arena.mark()()
+
+	var schemaPtr, columnPtr ptr_t
+	declTypePtr := c.arena.new(ptrlen)
+	collSeqPtr := c.arena.new(ptrlen)
+	notNullPtr := c.arena.new(ptrlen)
+	autoIncPtr := c.arena.new(ptrlen)
+	primaryKeyPtr := c.arena.new(ptrlen)
+	if schema != "" {
+		schemaPtr = c.arena.string(schema)
+	}
+	tablePtr := c.arena.string(table)
+	if column != "" {
+		columnPtr = c.arena.string(column)
+	}
+
+	rc := res_t(c.call("sqlite3_table_column_metadata", stk_t(c.handle),
+		stk_t(schemaPtr), stk_t(tablePtr), stk_t(columnPtr),
+		stk_t(declTypePtr), stk_t(collSeqPtr),
+		stk_t(notNullPtr), stk_t(primaryKeyPtr), stk_t(autoIncPtr)))
+	if err = c.error(rc); err == nil && column != "" {
+		if ptr := util.Read32[ptr_t](c.mod, declTypePtr); ptr != 0 {
+			declType = util.ReadString(c.mod, ptr, _MAX_NAME)
+		}
+		if ptr := util.Read32[ptr_t](c.mod, collSeqPtr); ptr != 0 {
+			collSeq = util.ReadString(c.mod, ptr, _MAX_NAME)
+		}
+		notNull = util.ReadBool(c.mod, notNullPtr)
+		autoInc = util.ReadBool(c.mod, autoIncPtr)
+		primaryKey = util.ReadBool(c.mod, primaryKeyPtr)
+	}
+	return
+}
+
+func (c *Conn) error(rc res_t, sql ...string) error {
 	return c.sqlite.error(rc, c.handle, sql...)
 }
 
-// DriverConn is implemented by the SQLite [database/sql] driver connection.
-//
-// It can be used to access SQLite features like [online backup].
-//
-// [online backup]: https://sqlite.org/backup.html
-type DriverConn interface {
-	Raw() *Conn
+func (c *Conn) stmtsIter(yield func(*Stmt) bool) {
+	for _, s := range c.stmts {
+		if !yield(s) {
+			break
+		}
+	}
 }

conn_iter.go

@@ -0,0 +1,11 @@
+//go:build go1.23
+
+package sqlite3
+
+import "iter"
+
+// Stmts returns an iterator for the prepared statements
+// associated with the database connection.
+//
+// https://sqlite.org/c3ref/next_stmt.html
+func (c *Conn) Stmts() iter.Seq[*Stmt] { return c.stmtsIter }

conn_old.go

@@ -0,0 +1,9 @@
+//go:build !go1.23
+
+package sqlite3
+
+// Stmts returns an iterator for the prepared statements
+// associated with the database connection.
+//
+// https://sqlite.org/c3ref/next_stmt.html
+func (c *Conn) Stmts() func(func(*Stmt) bool) { return c.stmtsIter }

const.go

@@ -1,21 +1,29 @@
 package sqlite3
 
-import "strconv"
+import (
+	"strconv"
+
+	"github.com/ncruces/go-sqlite3/internal/util"
+)
 
 const (
 	_OK   = 0   /* Successful result */
 	_ROW  = 100 /* sqlite3_step() has another row ready */
 	_DONE = 101 /* sqlite3_step() has finished executing */
 
-	_UTF8 = 1
+	_MAX_NAME         = 1e6 // Self-imposed limit for most NUL terminated strings.
+	_MAX_LENGTH       = 1e9
+	_MAX_SQL_LENGTH   = 1e9
+	_MAX_FUNCTION_ARG = 100
 
-	_MAX_NAME            = 1e6 // Self-imposed limit for most NUL terminated strings.
-	_MAX_LENGTH          = 1e9
-	_MAX_SQL_LENGTH      = 1e9
-	_MAX_ALLOCATION_SIZE = 0x7ffffeff
-	_MAX_FUNCTION_ARG    = 100
+	ptrlen = util.PtrLen
+	intlen = util.IntLen
+)
 
-	ptrlen = 4
+type (
+	stk_t = util.Stk_t
+	ptr_t = util.Ptr_t
+	res_t = util.Res_t
 )
 
 // ErrorCode is a result code that [Error.Code] might return.
@@ -109,7 +117,7 @@ const (
 	CANTOPEN_ISDIR          ExtendedErrorCode = xErrorCode(CANTOPEN) | (2 << 8)
 	CANTOPEN_FULLPATH       ExtendedErrorCode = xErrorCode(CANTOPEN) | (3 << 8)
 	CANTOPEN_CONVPATH       ExtendedErrorCode = xErrorCode(CANTOPEN) | (4 << 8)
-	CANTOPEN_DIRTYWAL       ExtendedErrorCode = xErrorCode(CANTOPEN) | (5 << 8) /* Not Used */
+	// CANTOPEN_DIRTYWAL    ExtendedErrorCode = xErrorCode(CANTOPEN) | (5 << 8) /* Not Used */
 	CANTOPEN_SYMLINK        ExtendedErrorCode = xErrorCode(CANTOPEN) | (6 << 8)
 	CORRUPT_VTAB            ExtendedErrorCode = xErrorCode(CORRUPT) | (1 << 8)
 	CORRUPT_SEQUENCE        ExtendedErrorCode = xErrorCode(CORRUPT) | (2 << 8)
@@ -168,6 +176,7 @@ const (
 	PREPARE_PERSISTENT PrepareFlag = 0x01
 	PREPARE_NORMALIZE  PrepareFlag = 0x02
 	PREPARE_NO_VTAB    PrepareFlag = 0x04
+	PREPARE_DONT_LOG   PrepareFlag = 0x10
 )
 
 // FunctionFlag is a flag that can be passed to
@@ -177,11 +186,12 @@ const (
 type FunctionFlag uint32
 
 const (
-	DETERMINISTIC  FunctionFlag = 0x000000800
-	DIRECTONLY     FunctionFlag = 0x000080000
-	SUBTYPE        FunctionFlag = 0x000100000
-	INNOCUOUS      FunctionFlag = 0x000200000
-	RESULT_SUBTYPE FunctionFlag = 0x001000000
+	DETERMINISTIC FunctionFlag = 0x000000800
+	DIRECTONLY    FunctionFlag = 0x000080000
+	INNOCUOUS     FunctionFlag = 0x000200000
+	SELFORDER1    FunctionFlag = 0x002000000
+	// SUBTYPE        FunctionFlag = 0x000100000
+	// RESULT_SUBTYPE FunctionFlag = 0x001000000
 )
 
 // StmtStatus name counter values associated with the [Stmt.Status] method.
@@ -201,6 +211,28 @@ const (
 	STMTSTATUS_MEMUSED       StmtStatus = 99
 )
 
+// DBStatus are the available "verbs" that can be passed to the [Conn.Status] method.
+//
+// https://sqlite.org/c3ref/c_dbstatus_options.html
+type DBStatus uint32
+
+const (
+	DBSTATUS_LOOKASIDE_USED      DBStatus = 0
+	DBSTATUS_CACHE_USED          DBStatus = 1
+	DBSTATUS_SCHEMA_USED         DBStatus = 2
+	DBSTATUS_STMT_USED           DBStatus = 3
+	DBSTATUS_LOOKASIDE_HIT       DBStatus = 4
+	DBSTATUS_LOOKASIDE_MISS_SIZE DBStatus = 5
+	DBSTATUS_LOOKASIDE_MISS_FULL DBStatus = 6
+	DBSTATUS_CACHE_HIT           DBStatus = 7
+	DBSTATUS_CACHE_MISS          DBStatus = 8
+	DBSTATUS_CACHE_WRITE         DBStatus = 9
+	DBSTATUS_DEFERRED_FKS        DBStatus = 10
+	DBSTATUS_CACHE_USED_SHARED   DBStatus = 11
+	DBSTATUS_CACHE_SPILL         DBStatus = 12
+	// DBSTATUS_MAX              DBStatus = 12
+)
+
 // DBConfig are the available database connection configuration options.
 //
 // https://sqlite.org/c3ref/c_dbconfig_defensive.html
@@ -227,6 +259,28 @@ const (
 	DBCONFIG_TRUSTED_SCHEMA        DBConfig = 1017
 	DBCONFIG_STMT_SCANSTATUS       DBConfig = 1018
 	DBCONFIG_REVERSE_SCANORDER     DBConfig = 1019
+	DBCONFIG_ENABLE_ATTACH_CREATE  DBConfig = 1020
+	DBCONFIG_ENABLE_ATTACH_WRITE   DBConfig = 1021
+	DBCONFIG_ENABLE_COMMENTS       DBConfig = 1022
+	// DBCONFIG_MAX                DBConfig = 1022
+)
+
+// FcntlOpcode are the available opcodes for [Conn.FileControl].
+//
+// https://sqlite.org/c3ref/c_fcntl_begin_atomic_write.html
+type FcntlOpcode uint32
+
+const (
+	FCNTL_LOCKSTATE           FcntlOpcode = 1
+	FCNTL_CHUNK_SIZE          FcntlOpcode = 6
+	FCNTL_FILE_POINTER        FcntlOpcode = 7
+	FCNTL_PERSIST_WAL         FcntlOpcode = 10
+	FCNTL_POWERSAFE_OVERWRITE FcntlOpcode = 13
+	FCNTL_VFS_POINTER         FcntlOpcode = 27
+	FCNTL_JOURNAL_POINTER     FcntlOpcode = 28
+	FCNTL_DATA_VERSION        FcntlOpcode = 35
+	FCNTL_RESERVE_BYTES       FcntlOpcode = 38
+	FCNTL_RESET_CACHE         FcntlOpcode = 42
 )
 
 // LimitCategory are the available run-time limit categories.
@@ -289,8 +343,8 @@ const (
 	AUTH_DROP_VTABLE         AuthorizerActionCode = 30 /* Table Name      Module Name     */
 	AUTH_FUNCTION            AuthorizerActionCode = 31 /* NULL            Function Name   */
 	AUTH_SAVEPOINT           AuthorizerActionCode = 32 /* Operation       Savepoint Name  */
-	AUTH_COPY                AuthorizerActionCode = 0  /* No longer used */
 	AUTH_RECURSIVE           AuthorizerActionCode = 33 /* NULL            NULL            */
+	// AUTH_COPY             AuthorizerActionCode = 0  /* No longer used */
 )
 
 // AuthorizerReturnCode are the integer codes
@@ -328,6 +382,18 @@ const (
 	TXN_WRITE TxnState = 2
 )
 
+// TraceEvent identify classes of events that can be monitored with [Conn.Trace].
+//
+// https://sqlite.org/c3ref/c_trace.html
+type TraceEvent uint32
+
+const (
+	TRACE_STMT    TraceEvent = 0x01
+	TRACE_PROFILE TraceEvent = 0x02
+	TRACE_ROW     TraceEvent = 0x04
+	TRACE_CLOSE   TraceEvent = 0x08
+)
+
 // Datatype is a fundamental datatype of SQLite.
 //
 // https://sqlite.org/c3ref/c_blob.html

context.go

@@ -15,7 +15,7 @@ import (
 // https://sqlite.org/c3ref/context.html
 type Context struct {
 	c      *Conn
-	handle uint32
+	handle ptr_t
 }
 
 // Conn returns the database connection of the
@@ -32,14 +32,14 @@ func (ctx Context) Conn() *Conn {
 // https://sqlite.org/c3ref/get_auxdata.html
 func (ctx Context) SetAuxData(n int, data any) {
 	ptr := util.AddHandle(ctx.c.ctx, data)
-	ctx.c.call("sqlite3_set_auxdata_go", uint64(ctx.handle), uint64(n), uint64(ptr))
+	ctx.c.call("sqlite3_set_auxdata_go", stk_t(ctx.handle), stk_t(n), stk_t(ptr))
 }
 
 // GetAuxData returns metadata for argument n of the function.
 //
 // https://sqlite.org/c3ref/get_auxdata.html
 func (ctx Context) GetAuxData(n int) any {
-	ptr := uint32(ctx.c.call("sqlite3_get_auxdata", uint64(ctx.handle), uint64(n)))
+	ptr := ptr_t(ctx.c.call("sqlite3_get_auxdata", stk_t(ctx.handle), stk_t(n)))
 	return util.GetHandle(ctx.c.ctx, ptr)
 }
 
@@ -68,7 +68,7 @@ func (ctx Context) ResultInt(value int) {
 // https://sqlite.org/c3ref/result_blob.html
 func (ctx Context) ResultInt64(value int64) {
 	ctx.c.call("sqlite3_result_int64",
-		uint64(ctx.handle), uint64(value))
+		stk_t(ctx.handle), stk_t(value))
 }
 
 // ResultFloat sets the result of the function to a float64.
@@ -76,7 +76,7 @@ func (ctx Context) ResultInt64(value int64) {
 // https://sqlite.org/c3ref/result_blob.html
 func (ctx Context) ResultFloat(value float64) {
 	ctx.c.call("sqlite3_result_double",
-		uint64(ctx.handle), math.Float64bits(value))
+		stk_t(ctx.handle), stk_t(math.Float64bits(value)))
 }
 
 // ResultText sets the result of the function to a string.
@@ -84,19 +84,18 @@ func (ctx Context) ResultFloat(value float64) {
 // https://sqlite.org/c3ref/result_blob.html
 func (ctx Context) ResultText(value string) {
 	ptr := ctx.c.newString(value)
-	ctx.c.call("sqlite3_result_text64",
-		uint64(ctx.handle), uint64(ptr), uint64(len(value)),
-		uint64(ctx.c.freer), _UTF8)
+	ctx.c.call("sqlite3_result_text_go",
+		stk_t(ctx.handle), stk_t(ptr), stk_t(len(value)))
 }
 
 // ResultRawText sets the text result of the function to a []byte.
+// Returning a nil slice is the same as calling [Context.ResultNull].
 //
 // https://sqlite.org/c3ref/result_blob.html
 func (ctx Context) ResultRawText(value []byte) {
 	ptr := ctx.c.newBytes(value)
-	ctx.c.call("sqlite3_result_text64",
-		uint64(ctx.handle), uint64(ptr), uint64(len(value)),
-		uint64(ctx.c.freer), _UTF8)
+	ctx.c.call("sqlite3_result_text_go",
+		stk_t(ctx.handle), stk_t(ptr), stk_t(len(value)))
 }
 
 // ResultBlob sets the result of the function to a []byte.
@@ -105,9 +104,8 @@ func (ctx Context) ResultRawText(value []byte) {
 // https://sqlite.org/c3ref/result_blob.html
 func (ctx Context) ResultBlob(value []byte) {
 	ptr := ctx.c.newBytes(value)
-	ctx.c.call("sqlite3_result_blob64",
-		uint64(ctx.handle), uint64(ptr), uint64(len(value)),
-		uint64(ctx.c.freer))
+	ctx.c.call("sqlite3_result_blob_go",
+		stk_t(ctx.handle), stk_t(ptr), stk_t(len(value)))
 }
 
 // ResultZeroBlob sets the result of the function to a zero-filled, length n BLOB.
@@ -115,7 +113,7 @@ func (ctx Context) ResultBlob(value []byte) {
 // https://sqlite.org/c3ref/result_blob.html
 func (ctx Context) ResultZeroBlob(n int64) {
 	ctx.c.call("sqlite3_result_zeroblob64",
-		uint64(ctx.handle), uint64(n))
+		stk_t(ctx.handle), stk_t(n))
 }
 
 // ResultNull sets the result of the function to NULL.
@@ -123,14 +121,15 @@ func (ctx Context) ResultZeroBlob(n int64) {
 // https://sqlite.org/c3ref/result_blob.html
 func (ctx Context) ResultNull() {
 	ctx.c.call("sqlite3_result_null",
-		uint64(ctx.handle))
+		stk_t(ctx.handle))
 }
 
 // ResultTime sets the result of the function to a [time.Time].
 //
 // https://sqlite.org/c3ref/result_blob.html
 func (ctx Context) ResultTime(value time.Time, format TimeFormat) {
-	if format == TimeFormatDefault {
+	switch format {
+	case TimeFormatDefault, TimeFormatAuto, time.RFC3339Nano:
 		ctx.resultRFC3339Nano(value)
 		return
 	}
@@ -147,15 +146,14 @@ func (ctx Context) ResultTime(value time.Time, format TimeFormat) {
 }
 
 func (ctx Context) resultRFC3339Nano(value time.Time) {
-	const maxlen = uint64(len(time.RFC3339Nano)) + 5
+	const maxlen = int64(len(time.RFC3339Nano)) + 5
 
 	ptr := ctx.c.new(maxlen)
 	buf := util.View(ctx.c.mod, ptr, maxlen)
 	buf = value.AppendFormat(buf[:0], time.RFC3339Nano)
 
-	ctx.c.call("sqlite3_result_text64",
-		uint64(ctx.handle), uint64(ptr), uint64(len(buf)),
-		uint64(ctx.c.freer), _UTF8)
+	ctx.c.call("sqlite3_result_text_go",
+		stk_t(ctx.handle), stk_t(ptr), stk_t(len(buf)))
 }
 
 // ResultPointer sets the result of the function to NULL, just like [Context.ResultNull],
@@ -165,7 +163,8 @@ func (ctx Context) resultRFC3339Nano(value time.Time) {
 // https://sqlite.org/c3ref/result_blob.html
 func (ctx Context) ResultPointer(ptr any) {
 	valPtr := util.AddHandle(ctx.c.ctx, ptr)
-	ctx.c.call("sqlite3_result_pointer_go", uint64(valPtr))
+	ctx.c.call("sqlite3_result_pointer_go",
+		stk_t(ctx.handle), stk_t(valPtr))
 }
 
 // ResultJSON sets the result of the function to the JSON encoding of value.
@@ -175,7 +174,7 @@ func (ctx Context) ResultJSON(value any) {
 	data, err := json.Marshal(value)
 	if err != nil {
 		ctx.ResultError(err)
-		return
+		return // notest
 	}
 	ctx.ResultRawText(data)
 }
@@ -189,7 +188,7 @@ func (ctx Context) ResultValue(value Value) {
 		return
 	}
 	ctx.c.call("sqlite3_result_value",
-		uint64(ctx.handle), uint64(value.handle))
+		stk_t(ctx.handle), stk_t(value.handle))
 }
 
 // ResultError sets the result of the function an error.
@@ -197,12 +196,12 @@ func (ctx Context) ResultValue(value Value) {
 // https://sqlite.org/c3ref/result_blob.html
 func (ctx Context) ResultError(err error) {
 	if errors.Is(err, NOMEM) {
-		ctx.c.call("sqlite3_result_error_nomem", uint64(ctx.handle))
+		ctx.c.call("sqlite3_result_error_nomem", stk_t(ctx.handle))
 		return
 	}
 
 	if errors.Is(err, TOOBIG) {
-		ctx.c.call("sqlite3_result_error_toobig", uint64(ctx.handle))
+		ctx.c.call("sqlite3_result_error_toobig", stk_t(ctx.handle))
 		return
 	}
 
@@ -211,11 +210,11 @@ func (ctx Context) ResultError(err error) {
 		defer ctx.c.arena.mark()()
 		ptr := ctx.c.arena.string(msg)
 		ctx.c.call("sqlite3_result_error",
-			uint64(ctx.handle), uint64(ptr), uint64(len(msg)))
+			stk_t(ctx.handle), stk_t(ptr), stk_t(len(msg)))
 	}
 	if code != _OK {
 		ctx.c.call("sqlite3_result_error_code",
-			uint64(ctx.handle), uint64(code))
+			stk_t(ctx.handle), stk_t(code))
 	}
 }
 
@@ -224,6 +223,6 @@ func (ctx Context) ResultError(err error) {
 //
 // https://sqlite.org/c3ref/vtab_nochange.html
 func (ctx Context) VTabNoChange() bool {
-	r := ctx.c.call("sqlite3_vtab_nochange", uint64(ctx.handle))
-	return r != 0
+	b := int32(ctx.c.call("sqlite3_vtab_nochange", stk_t(ctx.handle)))
+	return b != 0
 }

driver/driver.go

@@ -8,21 +8,50 @@
 //
 // The data source name for "sqlite3" databases can be a filename or a "file:" [URI].
 //
+// # Default transaction mode
+//
 // The [TRANSACTION] mode can be specified using "_txlock":
 //
 //	sql.Open("sqlite3", "file:demo.db?_txlock=immediate")
 //
-// Possible values are: "deferred", "immediate", "exclusive".
-// A [read-only] transaction is always "deferred", regardless of "_txlock".
+// Possible values are: "deferred" (the default), "immediate", "exclusive".
+// Regardless of "_txlock":
+//   - a [linearizable] transaction is always "exclusive";
+//   - a [serializable] transaction is always "immediate";
+//   - a [read-only] transaction is always "deferred".
+//
+// # Working with time
 //
 // The time encoding/decoding format can be specified using "_timefmt":
 //
 //	sql.Open("sqlite3", "file:demo.db?_timefmt=sqlite")
 //
 // Possible values are: "auto" (the default), "sqlite", "rfc3339";
-// "auto" encodes as RFC 3339 and decodes any [format] supported by SQLite;
-// "sqlite" encodes as SQLite and decodes any [format] supported by SQLite;
-// "rfc3339" encodes and decodes RFC 3339 only.
+//   - "auto" encodes as RFC 3339 and decodes any [format] supported by SQLite;
+//   - "sqlite" encodes as SQLite and decodes any [format] supported by SQLite;
+//   - "rfc3339" encodes and decodes RFC 3339 only.
+//
+// If you encode as RFC 3339 (the default),
+// consider using the TIME [collating sequence] to produce a time-ordered sequence.
+//
+// To scan values in other formats, [sqlite3.TimeFormat.Scanner] may be helpful.
+// To bind values in other formats, [sqlite3.TimeFormat.Encode] them before binding.
+//
+// When using a custom time struct, you'll have to implement
+// [database/sql/driver.Valuer] and [database/sql.Scanner].
+//
+// The Value method should ideally encode to a time [format] supported by SQLite.
+// This ensures SQL date and time functions work as they should,
+// and that your schema works with other SQLite tools.
+// [sqlite3.TimeFormat.Encode] may help.
+//
+// The Scan method needs to take into account that the value it receives can be of differing types.
+// It can already be a [time.Time], if the driver decoded the value according to "_timefmt" rules.
+// Or it can be a: string, int64, float64, []byte, or nil,
+// depending on the column type and what whoever wrote the value.
+// [sqlite3.TimeFormat.Decode] may help.
+//
+// # Setting PRAGMAs
 //
 // [PRAGMA] statements can be specified using "_pragma":
 //
@@ -31,13 +60,17 @@
 // If no PRAGMAs are specified, a busy timeout of 1 minute is set.
 //
 // Order matters:
-// busy timeout and locking mode should be the first PRAGMAs set, in that order.
+// encryption keys, busy timeout and locking mode should be the first PRAGMAs set,
+// in that order.
 //
 // [URI]: https://sqlite.org/uri.html
 // [PRAGMA]: https://sqlite.org/pragma.html
-// [format]: https://sqlite.org/lang_datefunc.html#time_values
 // [TRANSACTION]: https://sqlite.org/lang_transaction.html#deferred_immediate_and_exclusive_transactions
+// [linearizable]: https://pkg.go.dev/database/sql#TxOptions
+// [serializable]: https://pkg.go.dev/database/sql#TxOptions
 // [read-only]: https://pkg.go.dev/database/sql#TxOptions
+// [format]: https://sqlite.org/lang_datefunc.html#time_values
+// [collating sequence]: https://sqlite.org/datatype3.html#collating_sequences
 package driver
 
 import (
@@ -48,6 +81,7 @@ import (
 	"fmt"
 	"io"
 	"net/url"
+	"reflect"
 	"strings"
 	"time"
 	"unsafe"
@@ -69,11 +103,22 @@ func init() {
 
 // Open opens the SQLite database specified by dataSourceName as a [database/sql.DB].
 //
-// The init function is called by the driver on new connections.
+// Open accepts zero, one, or two callbacks (nil callbacks are ignored).
+// The first callback is called when the driver opens a new connection.
+// The second callback is called before the driver closes a connection.
 // The [sqlite3.Conn] can be used to execute queries, register functions, etc.
-// Any error returned closes the connection and is returned to [database/sql].
-func Open(dataSourceName string, init func(*sqlite3.Conn) error) (*sql.DB, error) {
-	c, err := (&SQLite{Init: init}).OpenConnector(dataSourceName)
+func Open(dataSourceName string, fn ...func(*sqlite3.Conn) error) (*sql.DB, error) {
+	if len(fn) > 2 {
+		return nil, sqlite3.MISUSE
+	}
+	var init, term func(*sqlite3.Conn) error
+	if len(fn) > 1 {
+		term = fn[1]
+	}
+	if len(fn) > 0 {
+		init = fn[0]
+	}
+	c, err := newConnector(dataSourceName, init, term)
 	if err != nil {
 		return nil, err
 	}
@@ -81,16 +126,16 @@ func Open(dataSourceName string, init func(*sqlite3.Conn) error) (*sql.DB, error
 }
 
 // SQLite implements [database/sql/driver.Driver].
-type SQLite struct {
-	// Init function is called by the driver on new connections.
-	// The [sqlite3.Conn] can be used to execute queries, register functions, etc.
-	// Any error returned closes the connection and is returned to [database/sql].
-	Init func(*sqlite3.Conn) error
-}
+type SQLite struct{}
+
+var (
+	// Ensure these interfaces are implemented:
+	_ driver.DriverContext = &SQLite{}
+)
 
 // Open implements [database/sql/driver.Driver].
 func (d *SQLite) Open(name string) (driver.Conn, error) {
-	c, err := d.newConnector(name)
+	c, err := newConnector(name, nil, nil)
 	if err != nil {
 		return nil, err
 	}
@@ -99,11 +144,11 @@ func (d *SQLite) Open(name string) (driver.Conn, error) {
 
 // OpenConnector implements [database/sql/driver.DriverContext].
 func (d *SQLite) OpenConnector(name string) (driver.Connector, error) {
-	return d.newConnector(name)
+	return newConnector(name, nil, nil)
 }
 
-func (d *SQLite) newConnector(name string) (*connector, error) {
-	c := connector{driver: d, name: name}
+func newConnector(name string, init, term func(*sqlite3.Conn) error) (*connector, error) {
+	c := connector{name: name, init: init, term: term}
 
 	var txlock, timefmt string
 	if strings.HasPrefix(name, "file:") {
@@ -119,10 +164,8 @@ func (d *SQLite) newConnector(name string) (*connector, error) {
 	}
 
 	switch txlock {
-	case "":
-		c.txBegin = "BEGIN"
-	case "deferred", "immediate", "exclusive":
-		c.txBegin = "BEGIN " + txlock
+	case "", "deferred", "concurrent", "immediate", "exclusive":
+		c.txLock = txlock
 	default:
 		return nil, fmt.Errorf("sqlite3: invalid _txlock: %s", txlock)
 	}
@@ -145,31 +188,32 @@ func (d *SQLite) newConnector(name string) (*connector, error) {
 }
 
 type connector struct {
-	driver  *SQLite
+	init    func(*sqlite3.Conn) error
+	term    func(*sqlite3.Conn) error
 	name    string
-	txBegin string
+	txLock  string
 	tmRead  sqlite3.TimeFormat
 	tmWrite sqlite3.TimeFormat
 	pragmas bool
 }
 
 func (n *connector) Driver() driver.Driver {
-	return n.driver
+	return &SQLite{}
 }
 
-func (n *connector) Connect(ctx context.Context) (_ driver.Conn, err error) {
+func (n *connector) Connect(ctx context.Context) (ret driver.Conn, err error) {
 	c := &conn{
-		txBegin: n.txBegin,
+		txLock:  n.txLock,
 		tmRead:  n.tmRead,
 		tmWrite: n.tmWrite,
 	}
 
-	c.Conn, err = sqlite3.Open(n.name)
+	c.Conn, err = sqlite3.OpenContext(ctx, n.name)
 	if err != nil {
 		return nil, err
 	}
 	defer func() {
-		if err != nil {
+		if ret == nil {
 			c.Close()
 		}
 	}()
@@ -178,22 +222,23 @@ func (n *connector) Connect(ctx context.Context) (_ driver.Conn, err error) {
 	defer c.Conn.SetInterrupt(old)
 
 	if !n.pragmas {
-		err = c.Conn.BusyTimeout(60 * time.Second)
+		err = c.Conn.BusyTimeout(time.Minute)
 		if err != nil {
 			return nil, err
 		}
 	}
-	if n.driver.Init != nil {
-		err = n.driver.Init(c.Conn)
+	if n.init != nil {
+		err = n.init(c.Conn)
 		if err != nil {
 			return nil, err
 		}
 	}
-	if n.pragmas || n.driver.Init != nil {
+	if n.pragmas || n.init != nil {
 		s, _, err := c.Conn.Prepare(`PRAGMA query_only`)
 		if err != nil {
 			return nil, err
 		}
+		defer s.Close()
 		if s.Step() && s.ColumnBool(0) {
 			c.readOnly = '1'
 		} else {
@@ -204,25 +249,62 @@ func (n *connector) Connect(ctx context.Context) (_ driver.Conn, err error) {
 			return nil, err
 		}
 	}
+	if n.term != nil {
+		err = c.Conn.Trace(sqlite3.TRACE_CLOSE, func(sqlite3.TraceEvent, any, any) error {
+			return n.term(c.Conn)
+		})
+		if err != nil {
+			return nil, err
+		}
+	}
 	return c, nil
 }
 
+// Conn is implemented by the SQLite [database/sql] driver connections.
+//
+// It can be used to access SQLite features like [online backup]:
+//
+//	db, err := driver.Open("temp.db")
+//	if err != nil {
+//		log.Fatal(err)
+//	}
+//	defer db.Close()
+//
+//	conn, err := db.Conn(context.TODO())
+//	if err != nil {
+//		log.Fatal(err)
+//	}
+//	defer conn.Close()
+//
+//	err = conn.Raw(func(driverConn any) error {
+//		conn := driverConn.(driver.Conn)
+//		return conn.Raw().Backup("main", "backup.db")
+//	})
+//	if err != nil {
+//		log.Fatal(err)
+//	}
+//
+// [online backup]: https://sqlite.org/backup.html
+type Conn interface {
+	Raw() *sqlite3.Conn
+	driver.Conn
+	driver.ConnBeginTx
+	driver.ConnPrepareContext
+}
+
 type conn struct {
 	*sqlite3.Conn
-	txBegin    string
-	txCommit   string
-	txRollback string
-	tmRead     sqlite3.TimeFormat
-	tmWrite    sqlite3.TimeFormat
-	readOnly   byte
+	txLock   string
+	txReset  string
+	tmRead   sqlite3.TimeFormat
+	tmWrite  sqlite3.TimeFormat
+	readOnly byte
 }
 
 var (
 	// Ensure these interfaces are implemented:
-	_ driver.ConnPrepareContext = &conn{}
-	_ driver.ExecerContext      = &conn{}
-	_ driver.ConnBeginTx        = &conn{}
-	_ sqlite3.DriverConn        = &conn{}
+	_ Conn                 = &conn{}
+	_ driver.ExecerContext = &conn{}
 )
 
 func (c *conn) Raw() *sqlite3.Conn {
@@ -231,31 +313,30 @@ func (c *conn) Raw() *sqlite3.Conn {
 
 // Deprecated: use BeginTx instead.
 func (c *conn) Begin() (driver.Tx, error) {
+	// notest
 	return c.BeginTx(context.Background(), driver.TxOptions{})
 }
 
 func (c *conn) BeginTx(ctx context.Context, opts driver.TxOptions) (driver.Tx, error) {
-	txBegin := c.txBegin
-	c.txCommit = `COMMIT`
-	c.txRollback = `ROLLBACK`
-
-	if opts.ReadOnly {
-		txBegin = `
-			BEGIN deferred;
-			PRAGMA query_only=on`
-		c.txRollback = `
-			ROLLBACK;
-			PRAGMA query_only=` + string(c.readOnly)
-		c.txCommit = c.txRollback
-	}
-
+	var txLock string
 	switch opts.Isolation {
 	default:
 		return nil, util.IsolationErr
-	case
-		driver.IsolationLevel(sql.LevelDefault),
-		driver.IsolationLevel(sql.LevelSerializable):
-		break
+	case driver.IsolationLevel(sql.LevelLinearizable):
+		txLock = "exclusive"
+	case driver.IsolationLevel(sql.LevelSerializable):
+		txLock = "immediate"
+	case driver.IsolationLevel(sql.LevelDefault):
+		if !opts.ReadOnly {
+			txLock = c.txLock
+		}
+	}
+
+	c.txReset = ``
+	txBegin := `BEGIN ` + txLock
+	if opts.ReadOnly {
+		txBegin += ` ; PRAGMA query_only=on`
+		c.txReset = `; PRAGMA query_only=` + string(c.readOnly)
 	}
 
 	old := c.Conn.SetInterrupt(ctx)
@@ -269,7 +350,7 @@ func (c *conn) BeginTx(ctx context.Context, opts driver.TxOptions) (driver.Tx, e
 }
 
 func (c *conn) Commit() error {
-	err := c.Conn.Exec(c.txCommit)
+	err := c.Conn.Exec(`COMMIT` + c.txReset)
 	if err != nil && !c.Conn.GetAutocommit() {
 		c.Rollback()
 	}
@@ -277,16 +358,17 @@ func (c *conn) Commit() error {
 }
 
 func (c *conn) Rollback() error {
-	err := c.Conn.Exec(c.txRollback)
+	err := c.Conn.Exec(`ROLLBACK` + c.txReset)
 	if errors.Is(err, sqlite3.INTERRUPT) {
 		old := c.Conn.SetInterrupt(context.Background())
 		defer c.Conn.SetInterrupt(old)
-		err = c.Conn.Exec(c.txRollback)
+		err = c.Conn.Exec(`ROLLBACK` + c.txReset)
 	}
 	return err
 }
 
 func (c *conn) Prepare(query string) (driver.Stmt, error) {
+	// notest
 	return c.PrepareContext(context.Background(), query)
 }
 
@@ -298,7 +380,7 @@ func (c *conn) PrepareContext(ctx context.Context, query string) (driver.Stmt, e
 	if err != nil {
 		return nil, err
 	}
-	if tail != "" {
+	if notWhitespace(tail) {
 		s.Close()
 		return nil, util.TailErr
 	}
@@ -329,6 +411,8 @@ func (c *conn) ExecContext(ctx context.Context, query string, args []driver.Name
 }
 
 func (c *conn) CheckNamedValue(arg *driver.NamedValue) error {
+	// Fast path: short circuit argument verification.
+	// Arguments will be rejected by conn.ExecContext.
 	return nil
 }
 
@@ -363,11 +447,13 @@ func (s *stmt) NumInput() int {
 
 // Deprecated: use ExecContext instead.
 func (s *stmt) Exec(args []driver.Value) (driver.Result, error) {
+	// notest
 	return s.ExecContext(context.Background(), namedValues(args))
 }
 
 // Deprecated: use QueryContext instead.
 func (s *stmt) Query(args []driver.Value) (driver.Rows, error) {
+	// notest
 	return s.QueryContext(context.Background(), namedValues(args))
 }
 
@@ -380,7 +466,9 @@ func (s *stmt) ExecContext(ctx context.Context, args []driver.NamedValue) (drive
 	old := s.Stmt.Conn().SetInterrupt(ctx)
 	defer s.Stmt.Conn().SetInterrupt(old)
 
-	err = s.Stmt.Exec()
+	err = errors.Join(
+		s.Stmt.Exec(),
+		s.Stmt.ClearBindings())
 	if err != nil {
 		return nil, err
 	}
@@ -403,7 +491,7 @@ func (s *stmt) setupBindings(args []driver.NamedValue) (err error) {
 		if arg.Name == "" {
 			ids = append(ids, arg.Ordinal)
 		} else {
-			for _, prefix := range []string{":", "@", "$"} {
+			for _, prefix := range [...]string{":", "@", "$"} {
 				if id := s.Stmt.BindIndex(prefix + arg.Name); id != 0 {
 					ids = append(ids, id)
 				}
@@ -437,9 +525,9 @@ func (s *stmt) setupBindings(args []driver.NamedValue) (err error) {
 			default:
 				panic(util.AssertErr())
 			}
-		}
-		if err != nil {
-			return err
+			if err != nil {
+				return err
+			}
 		}
 	}
 	return nil
@@ -493,37 +581,101 @@ type rows struct {
 	*stmt
 	names []string
 	types []string
+	nulls []bool
+	scans []scantype
 }
 
+type scantype byte
+
+const (
+	_ANY  scantype = iota
+	_INT  scantype = scantype(sqlite3.INTEGER)
+	_REAL scantype = scantype(sqlite3.FLOAT)
+	_TEXT scantype = scantype(sqlite3.TEXT)
+	_BLOB scantype = scantype(sqlite3.BLOB)
+	_NULL scantype = scantype(sqlite3.NULL)
+	_BOOL scantype = iota
+	_TIME
+)
+
+var (
+	// Ensure these interfaces are implemented:
+	_ driver.RowsColumnTypeDatabaseTypeName = &rows{}
+	_ driver.RowsColumnTypeNullable         = &rows{}
+)
+
 func (r *rows) Close() error {
-	r.Stmt.ClearBindings()
-	return r.Stmt.Reset()
+	return errors.Join(
+		r.Stmt.Reset(),
+		r.Stmt.ClearBindings())
 }
 
 func (r *rows) Columns() []string {
 	if r.names == nil {
 		count := r.Stmt.ColumnCount()
-		r.names = make([]string, count)
-		for i := range r.names {
-			r.names[i] = r.Stmt.ColumnName(i)
+		names := make([]string, count)
+		for i := range names {
+			names[i] = r.Stmt.ColumnName(i)
 		}
+		r.names = names
 	}
 	return r.names
 }
 
+func (r *rows) loadColumnMetadata() {
+	if r.nulls == nil {
+		count := r.Stmt.ColumnCount()
+		nulls := make([]bool, count)
+		types := make([]string, count)
+		scans := make([]scantype, count)
+		for i := range nulls {
+			if col := r.Stmt.ColumnOriginName(i); col != "" {
+				types[i], _, nulls[i], _, _, _ = r.Stmt.Conn().TableColumnMetadata(
+					r.Stmt.ColumnDatabaseName(i),
+					r.Stmt.ColumnTableName(i),
+					col)
+				types[i] = strings.ToUpper(types[i])
+				// These types are only used before we have rows,
+				// and otherwise as type hints.
+				// The first few ensure STRICT tables are strictly typed.
+				// The other two are type hints for booleans and time.
+				switch types[i] {
+				case "INT", "INTEGER":
+					scans[i] = _INT
+				case "REAL":
+					scans[i] = _REAL
+				case "TEXT":
+					scans[i] = _TEXT
+				case "BLOB":
+					scans[i] = _BLOB
+				case "BOOLEAN":
+					scans[i] = _BOOL
+				case "DATE", "TIME", "DATETIME", "TIMESTAMP":
+					scans[i] = _TIME
+				}
+			}
+		}
+		r.nulls = nulls
+		r.types = types
+		r.scans = scans
+	}
+}
+
 func (r *rows) declType(index int) string {
 	if r.types == nil {
 		count := r.Stmt.ColumnCount()
-		r.types = make([]string, count)
-		for i := range r.types {
-			r.types[i] = strings.ToUpper(r.Stmt.ColumnDeclType(i))
+		types := make([]string, count)
+		for i := range types {
+			types[i] = strings.ToUpper(r.Stmt.ColumnDeclType(i))
 		}
+		r.types = types
 	}
 	return r.types[index]
 }
 
 func (r *rows) ColumnTypeDatabaseTypeName(index int) string {
-	decltype := r.declType(index)
+	r.loadColumnMetadata()
+	decltype := r.types[index]
 	if len := len(decltype); len > 0 && decltype[len-1] == ')' {
 		if i := strings.LastIndexByte(decltype, '('); i >= 0 {
 			decltype = decltype[:i]
@@ -532,6 +684,58 @@ func (r *rows) ColumnTypeDatabaseTypeName(index int) string {
 	return strings.TrimSpace(decltype)
 }
 
+func (r *rows) ColumnTypeNullable(index int) (nullable, ok bool) {
+	r.loadColumnMetadata()
+	if r.nulls[index] {
+		return false, true
+	}
+	return true, false
+}
+
+func (r *rows) ColumnTypeScanType(index int) (typ reflect.Type) {
+	r.loadColumnMetadata()
+	scan := r.scans[index]
+
+	if r.Stmt.Busy() {
+		// SQLite is dynamically typed and we now have a row.
+		// Always use the type of the value itself,
+		// unless the scan type is more specific
+		// and can scan the actual value.
+		val := scantype(r.Stmt.ColumnType(index))
+		useValType := true
+		switch {
+		case scan == _TIME && val != _BLOB && val != _NULL:
+			t := r.Stmt.ColumnTime(index, r.tmRead)
+			useValType = t == time.Time{}
+		case scan == _BOOL && val == _INT:
+			i := r.Stmt.ColumnInt64(index)
+			useValType = i != 0 && i != 1
+		case scan == _BLOB && val == _NULL:
+			useValType = false
+		}
+		if useValType {
+			scan = val
+		}
+	}
+
+	switch scan {
+	case _INT:
+		return reflect.TypeFor[int64]()
+	case _REAL:
+		return reflect.TypeFor[float64]()
+	case _TEXT:
+		return reflect.TypeFor[string]()
+	case _BLOB:
+		return reflect.TypeFor[[]byte]()
+	case _BOOL:
+		return reflect.TypeFor[bool]()
+	case _TIME:
+		return reflect.TypeFor[time.Time]()
+	default:
+		return reflect.TypeFor[any]()
+	}
+}
+
 func (r *rows) Next(dest []driver.Value) error {
 	old := r.Stmt.Conn().SetInterrupt(r.ctx)
 	defer r.Stmt.Conn().SetInterrupt(old)
@@ -544,30 +748,27 @@ func (r *rows) Next(dest []driver.Value) error {
 	}
 
 	data := unsafe.Slice((*any)(unsafe.SliceData(dest)), len(dest))
-	err := r.Stmt.Columns(data)
+	err := r.Stmt.Columns(data...)
 	for i := range dest {
 		if t, ok := r.decodeTime(i, dest[i]); ok {
 			dest[i] = t
-			continue
-		}
-		if s, ok := dest[i].(string); ok {
-			t, ok := maybeTime(s)
-			if ok {
-				dest[i] = t
-			}
 		}
 	}
 	return err
 }
 
 func (r *rows) decodeTime(i int, v any) (_ time.Time, ok bool) {
-	if r.tmRead == sqlite3.TimeFormatDefault {
-		// handled by maybeTime
-		return
-	}
-	switch v.(type) {
-	case int64, float64, string:
+	switch v := v.(type) {
+	case int64, float64:
 		// could be a time value
+	case string:
+		if r.tmWrite != "" && r.tmWrite != time.RFC3339 && r.tmWrite != time.RFC3339Nano {
+			break
+		}
+		t, ok := maybeTime(v)
+		if ok {
+			return t, true
+		}
 	default:
 		return
 	}

driver/driver_test.go

@@ -7,7 +7,7 @@ import (
 	"errors"
 	"math"
 	"net/url"
-	"path/filepath"
+	"reflect"
 	"testing"
 	"time"
 
@@ -15,9 +15,21 @@ import (
 	_ "github.com/ncruces/go-sqlite3/embed"
 	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
 	"github.com/ncruces/go-sqlite3/internal/util"
-	"github.com/ncruces/go-sqlite3/vfs"
+	"github.com/ncruces/go-sqlite3/vfs/memdb"
 )
 
+func Test_Open_error(t *testing.T) {
+	t.Parallel()
+
+	_, err := Open("", nil, nil, nil)
+	if err == nil {
+		t.Error("want error")
+	}
+	if !errors.Is(err, sqlite3.MISUSE) {
+		t.Errorf("got %v, want sqlite3.MISUSE", err)
+	}
+}
+
 func Test_Open_dir(t *testing.T) {
 	t.Parallel()
 
@@ -38,8 +50,11 @@ func Test_Open_dir(t *testing.T) {
 
 func Test_Open_pragma(t *testing.T) {
 	t.Parallel()
+	tmp := memdb.TestDB(t, url.Values{
+		"_pragma": {"busy_timeout(1000)"},
+	})
 
-	db, err := sql.Open("sqlite3", "file::memory:?_pragma=busy_timeout(1000)")
+	db, err := sql.Open("sqlite3", tmp)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -57,8 +72,11 @@ func Test_Open_pragma(t *testing.T) {
 
 func Test_Open_pragma_invalid(t *testing.T) {
 	t.Parallel()
+	tmp := memdb.TestDB(t, url.Values{
+		"_pragma": {"busy_timeout 1000"},
+	})
 
-	db, err := sql.Open("sqlite3", "file::memory:?_pragma=busy_timeout+1000")
+	db, err := sql.Open("sqlite3", tmp)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -81,14 +99,13 @@ func Test_Open_pragma_invalid(t *testing.T) {
 }
 
 func Test_Open_txLock(t *testing.T) {
-	if !vfs.SupportsFileLocking {
-		t.Skip("skipping without locks")
-	}
 	t.Parallel()
+	tmp := memdb.TestDB(t, url.Values{
+		"_txlock": {"exclusive"},
+		"_pragma": {"busy_timeout(1000)"},
+	})
 
-	db, err := sql.Open("sqlite3", "file:"+
-		filepath.ToSlash(filepath.Join(t.TempDir(), "test.db"))+
-		"?_txlock=exclusive&_pragma=busy_timeout(0)")
+	db, err := sql.Open("sqlite3", tmp)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -119,8 +136,11 @@ func Test_Open_txLock(t *testing.T) {
 
 func Test_Open_txLock_invalid(t *testing.T) {
 	t.Parallel()
+	tmp := memdb.TestDB(t, url.Values{
+		"_txlock": {"xclusive"},
+	})
 
-	_, err := sql.Open("sqlite3", "file::memory:?_txlock=xclusive")
+	_, err := sql.Open("sqlite3", tmp+"_txlock=xclusive")
 	if err == nil {
 		t.Fatal("want error")
 	}
@@ -130,17 +150,16 @@ func Test_Open_txLock_invalid(t *testing.T) {
 }
 
 func Test_BeginTx(t *testing.T) {
-	if !vfs.SupportsFileLocking {
-		t.Skip("skipping without locks")
-	}
 	t.Parallel()
+	tmp := memdb.TestDB(t, url.Values{
+		"_txlock": {"exclusive"},
+		"_pragma": {"busy_timeout(0)"},
+	})
 
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
-	db, err := sql.Open("sqlite3", "file:"+
-		filepath.ToSlash(filepath.Join(t.TempDir(), "test.db"))+
-		"?_txlock=exclusive&_pragma=busy_timeout(0)")
+	db, err := sql.Open("sqlite3", tmp)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -182,8 +201,9 @@ func Test_BeginTx(t *testing.T) {
 
 func Test_Prepare(t *testing.T) {
 	t.Parallel()
+	tmp := memdb.TestDB(t)
 
-	db, err := sql.Open("sqlite3", ":memory:")
+	db, err := sql.Open("sqlite3", tmp)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -205,8 +225,8 @@ func Test_Prepare(t *testing.T) {
 	}
 
 	_, err = db.Prepare(`SELECT 1; `)
-	if err.Error() != string(util.TailErr) {
-		t.Error("want tailErr")
+	if err != nil {
+		t.Error(err)
 	}
 
 	_, err = db.Prepare(`SELECT 1; SELECT`)
@@ -222,11 +242,12 @@ func Test_Prepare(t *testing.T) {
 
 func Test_QueryRow_named(t *testing.T) {
 	t.Parallel()
+	tmp := memdb.TestDB(t)
 
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
-	db, err := sql.Open("sqlite3", ":memory:")
+	db, err := sql.Open("sqlite3", tmp)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -274,8 +295,9 @@ func Test_QueryRow_named(t *testing.T) {
 
 func Test_QueryRow_blob_null(t *testing.T) {
 	t.Parallel()
+	tmp := memdb.TestDB(t)
 
-	db, err := sql.Open("sqlite3", ":memory:")
+	db, err := sql.Open("sqlite3", tmp)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -310,7 +332,11 @@ func Test_time(t *testing.T) {
 
 	for _, fmt := range []string{"auto", "sqlite", "rfc3339", time.ANSIC} {
 		t.Run(fmt, func(t *testing.T) {
-			db, err := sql.Open("sqlite3", "file::memory:?_timefmt="+url.QueryEscape(fmt))
+			tmp := memdb.TestDB(t, url.Values{
+				"_timefmt": {fmt},
+			})
+
+			db, err := sql.Open("sqlite3", tmp)
 			if err != nil {
 				t.Fatal(err)
 			}
@@ -340,3 +366,104 @@ func Test_time(t *testing.T) {
 		})
 	}
 }
+
+func Test_ColumnType_ScanType(t *testing.T) {
+	var (
+		INT  = reflect.TypeFor[int64]()
+		REAL = reflect.TypeFor[float64]()
+		TEXT = reflect.TypeFor[string]()
+		BLOB = reflect.TypeFor[[]byte]()
+		BOOL = reflect.TypeFor[bool]()
+		TIME = reflect.TypeFor[time.Time]()
+		ANY  = reflect.TypeFor[any]()
+	)
+
+	t.Parallel()
+	tmp := memdb.TestDB(t)
+
+	db, err := sql.Open("sqlite3", tmp)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	_, err = db.Exec(`
+		CREATE TABLE test (
+			col_int  INTEGER,
+			col_real REAL,
+			col_text TEXT,
+			col_blob BLOB,
+			col_bool BOOLEAN,
+			col_time DATETIME,
+			col_decimal DECIMAL
+		);
+		INSERT INTO test VALUES
+			(1, 1, 1, 1, 1, 1, 1),
+			(2.0, 2.0, 2.0, 2.0, 2.0, 2.0, 2.0),
+			('1', '1', '1', '1', '1', '1', '1'),
+			('x', 'x', 'x', 'x', 'x', 'x', 'x'),
+			(x'', x'', x'', x'', x'', x'', x''),
+			('2006-01-02T15:04:05Z', '2006-01-02T15:04:05Z', '2006-01-02T15:04:05Z', '2006-01-02T15:04:05Z',
+			 '2006-01-02T15:04:05Z', '2006-01-02T15:04:05Z', '2006-01-02T15:04:05Z'),
+			(TRUE, TRUE, TRUE, TRUE, TRUE, TRUE, TRUE),
+			(NULL, NULL, NULL, NULL, NULL, NULL, NULL);
+	`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rows, err := db.Query(`SELECT * FROM test`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer rows.Close()
+
+	cols, err := rows.ColumnTypes()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	want := [][]reflect.Type{
+		{INT, REAL, TEXT, BLOB, BOOL, TIME, ANY},
+		{INT, REAL, TEXT, INT, BOOL, TIME, INT},
+		{INT, REAL, TEXT, REAL, INT, TIME, INT},
+		{INT, REAL, TEXT, TEXT, BOOL, TIME, INT},
+		{TEXT, TEXT, TEXT, TEXT, TEXT, TEXT, TEXT},
+		{BLOB, BLOB, BLOB, BLOB, BLOB, BLOB, BLOB},
+		{TEXT, TEXT, TEXT, TEXT, TEXT, TIME, TEXT},
+		{INT, REAL, TEXT, INT, BOOL, TIME, INT},
+		{ANY, ANY, ANY, BLOB, ANY, ANY, ANY},
+	}
+	for j, c := range cols {
+		got := c.ScanType()
+		if got != want[0][j] {
+			t.Errorf("want %v, got %v, at column %d", want[0][j], got, j)
+		}
+	}
+
+	dest := make([]any, len(cols))
+	for i := 1; rows.Next(); i++ {
+		cols, err := rows.ColumnTypes()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		for j, c := range cols {
+			got := c.ScanType()
+			if got != want[i][j] {
+				t.Errorf("want %v, got %v, at row %d column %d", want[i][j], got, i, j)
+			}
+			dest[j] = reflect.New(got).Interface()
+		}
+
+		err = rows.Scan(dest...)
+		if err != nil {
+			t.Error(err)
+		}
+	}
+
+	err = rows.Err()
+	if err != nil {
+		t.Fatal(err)
+	}
+}

driver/example2_test.go

@@ -0,0 +1,144 @@
+//go:build linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock || sqlite3_dotlk
+
+package driver_test
+
+// Adapted from: https://go.dev/doc/tutorial/database-access
+
+import (
+	"database/sql"
+	"database/sql/driver"
+	"fmt"
+	"log"
+	"time"
+
+	"github.com/ncruces/go-sqlite3"
+	_ "github.com/ncruces/go-sqlite3/driver"
+	_ "github.com/ncruces/go-sqlite3/embed"
+	_ "github.com/ncruces/go-sqlite3/vfs/memdb"
+)
+
+func Example_customTime() {
+	db, err := sql.Open("sqlite3", "file:/time.db?vfs=memdb")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer db.Close()
+
+	_, err = db.Exec(`
+		CREATE TABLE data (
+			id INTEGER PRIMARY KEY,
+			date_time TEXT
+		) STRICT;
+	`)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// This one will be returned as string to [sql.Scanner] because it doesn't
+	// pass the driver's round-trip test when it tries to figure out if it's
+	// a time. 2009-11-17T20:34:58.650Z goes in, but parsing and formatting
+	// it with [time.RFC3338Nano] results in 2009-11-17T20:34:58.65Z. Though
+	// the times are identical, the trailing zero is lost in the string
+	// representation so the driver considers the conversion unsuccessful.
+	c1 := CustomTime{time.Date(
+		2009, 11, 17, 20, 34, 58, 650000000, time.UTC)}
+
+	// Store our custom time in the database.
+	_, err = db.Exec(`INSERT INTO data (date_time) VALUES(?)`, c1)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	var strc1 string
+	// Retrieve it as a string, the result of Value().
+	err = db.QueryRow(`
+		SELECT date_time
+		FROM data
+		WHERE id = last_insert_rowid()
+	`).Scan(&strc1)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println("in db:", strc1)
+
+	var resc1 CustomTime
+	// Retrieve it as our custom time type, going through Scan().
+	err = db.QueryRow(`
+		SELECT date_time
+		FROM data
+		WHERE id = last_insert_rowid()
+	`).Scan(&resc1)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println("custom time:", resc1)
+
+	// This one will be returned as [time.Time] to [sql.Scanner] because it does
+	// pass the driver's round-trip test when it tries to figure out if it's
+	// a time. 2009-11-17T20:34:58.651Z goes in, and parsing and formatting
+	// it with [time.RFC3339Nano] results in 2009-11-17T20:34:58.651Z.
+	c2 := CustomTime{time.Date(
+		2009, 11, 17, 20, 34, 58, 651000000, time.UTC)}
+	// Store our custom time in the database.
+	_, err = db.Exec(`INSERT INTO data (date_time) VALUES(?)`, c2)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	var strc2 string
+	// Retrieve it as a string, the result of Value().
+	err = db.QueryRow(`
+		SELECT date_time
+		FROM data
+		WHERE id = last_insert_rowid()
+	`).Scan(&strc2)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println("in db:", strc2)
+
+	var resc2 CustomTime
+	// Retrieve it as our custom time type, going through Scan().
+	err = db.QueryRow(`
+		SELECT date_time
+		FROM data
+		WHERE id = last_insert_rowid()
+	`).Scan(&resc2)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println("custom time:", resc2)
+	// Output:
+	// in db: 2009-11-17T20:34:58.650Z
+	// scan type string: 2009-11-17T20:34:58.650Z
+	// custom time: 2009-11-17 20:34:58.65 +0000 UTC
+	// in db: 2009-11-17T20:34:58.651Z
+	// scan type time: 2009-11-17 20:34:58.651 +0000 UTC
+	// custom time: 2009-11-17 20:34:58.651 +0000 UTC
+}
+
+type CustomTime struct{ time.Time }
+
+func (c CustomTime) Value() (driver.Value, error) {
+	return sqlite3.TimeFormat7TZ.Encode(c.UTC()), nil
+}
+
+func (c *CustomTime) Scan(value any) error {
+	switch v := value.(type) {
+	case nil:
+		*c = CustomTime{time.Time{}}
+	case time.Time:
+		fmt.Println("scan type time:", v)
+		*c = CustomTime{v}
+	case string:
+		fmt.Println("scan type string:", v)
+		t, err := sqlite3.TimeFormat7TZ.Decode(v)
+		if err != nil {
+			return err
+		}
+		*c = CustomTime{t}
+	default:
+		panic("unsupported value type")
+	}
+	return nil
+}

driver/example_test.go

@@ -1,4 +1,4 @@
-//go:build (linux || darwin || windows || freebsd || illumos) && !sqlite3_nosys
+//go:build linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock || sqlite3_dotlk
 
 package driver_test
 
@@ -12,6 +12,7 @@ import (
 
 	_ "github.com/ncruces/go-sqlite3/driver"
 	_ "github.com/ncruces/go-sqlite3/embed"
+	_ "github.com/ncruces/go-sqlite3/vfs/memdb"
 )
 
 var db *sql.DB

driver/json_test.go

@@ -11,7 +11,7 @@ import (
 )
 
 func Example_json() {
-	db, err := driver.Open("file:/test.db?vfs=memdb", nil)
+	db, err := driver.Open("file:/json.db?vfs=memdb")
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -21,8 +21,8 @@ func Example_json() {
 		CREATE TABLE orders (
 			cart_id INTEGER PRIMARY KEY,
 			user_id INTEGER NOT NULL,
-			cart    TEXT
-		);
+			cart    BLOB -- stored as JSONB
+		) STRICT;
 	`)
 	if err != nil {
 		log.Fatal(err)
@@ -39,7 +39,8 @@ func Example_json() {
 		Items []CartItem `json:"items"`
 	}
 
-	_, err = db.Exec(`INSERT INTO orders (user_id, cart) VALUES (?, ?)`, 123, sqlite3.JSON(Cart{
+	// convert to JSONB on insertion
+	_, err = db.Exec(`INSERT INTO orders (user_id, cart) VALUES (?, jsonb(?))`, 123, sqlite3.JSON(Cart{
 		[]CartItem{
 			{ItemID: "111", Name: "T-shirt", Quantity: 1, Price: 250},
 			{ItemID: "222", Name: "Trousers", Quantity: 1, Price: 600},
@@ -60,6 +61,24 @@ func Example_json() {
 	}
 
 	fmt.Println("total:", total)
+
+	var cart Cart
+	err = db.QueryRow(`
+		SELECT json(cart) -- convert to JSON on retrieval
+		FROM orders
+		WHERE cart_id = last_insert_rowid()
+	`).Scan(sqlite3.JSON(&cart))
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	for _, item := range cart.Items {
+		fmt.Printf("id: %s, name: %s, quantity: %d, price: %d\n",
+			item.ItemID, item.Name, item.Quantity, item.Price)
+	}
+
 	// Output:
 	// total: 850
+	// id: 111, name: T-shirt, quantity: 1, price: 250
+	// id: 222, name: Trousers, quantity: 1, price: 600
 }

driver/savepoint.go

@@ -16,12 +16,25 @@ func Savepoint(tx *sql.Tx) sqlite3.Savepoint {
 	return ctx.Savepoint
 }
 
+// A saveptCtx is never canceled, has no values, and has no deadline.
 type saveptCtx struct{ sqlite3.Savepoint }
 
-func (*saveptCtx) Deadline() (deadline time.Time, ok bool) { return }
+func (*saveptCtx) Deadline() (deadline time.Time, ok bool) {
+	// notest
+	return
+}
 
-func (*saveptCtx) Done() <-chan struct{} { return nil }
+func (*saveptCtx) Done() <-chan struct{} {
+	// notest
+	return nil
+}
 
-func (*saveptCtx) Err() error { return nil }
+func (*saveptCtx) Err() error {
+	// notest
+	return nil
+}
 
-func (*saveptCtx) Value(key any) any { return nil }
+func (*saveptCtx) Value(key any) any {
+	// notest
+	return nil
+}

driver/savepoint_test.go

@@ -6,11 +6,12 @@ import (
 
 	"github.com/ncruces/go-sqlite3/driver"
 	_ "github.com/ncruces/go-sqlite3/embed"
+	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
 	_ "github.com/ncruces/go-sqlite3/vfs/memdb"
 )
 
 func ExampleSavepoint() {
-	db, err := driver.Open("file:/test.db?vfs=memdb", nil)
+	db, err := driver.Open("file:/svpt.db?vfs=memdb")
 	if err != nil {
 		log.Fatal(err)
 	}

driver/time.go

@@ -1,8 +1,6 @@
 package driver
 
-import (
-	"time"
-)
+import "time"
 
 // Convert a string in [time.RFC3339Nano] format into a [time.Time]
 // if it roundtrips back to the same string.

driver/time_test.go

@@ -27,12 +27,12 @@ func Fuzz_stringOrTime_1(f *testing.F) {
 			// Make sure times round-trip to the same string:
 			// https://pkg.go.dev/database/sql#Rows.Scan
 			if v.Format(time.RFC3339Nano) != str {
-				t.Fatalf("did not round-trip: %q", str)
+				t.Errorf("did not round-trip: %q", str)
 			}
 		} else {
 			date, err := time.Parse(time.RFC3339Nano, str)
 			if err == nil && date.Format(time.RFC3339Nano) == str {
-				t.Fatalf("would round-trip: %q", str)
+				t.Errorf("would round-trip: %q", str)
 			}
 		}
 	})

driver/util.go

@@ -12,3 +12,63 @@ func namedValues(args []driver.Value) []driver.NamedValue {
 	}
 	return named
 }
+
+func notWhitespace(sql string) bool {
+	const (
+		code = iota
+		slash
+		minus
+		ccomment
+		sqlcomment
+		endcomment
+	)
+
+	state := code
+	for _, b := range ([]byte)(sql) {
+		if b == 0 {
+			break
+		}
+
+		switch state {
+		case code:
+			switch b {
+			case '/':
+				state = slash
+			case '-':
+				state = minus
+			case ' ', ';', '\t', '\n', '\v', '\f', '\r':
+				continue
+			default:
+				return true
+			}
+		case slash:
+			if b != '*' {
+				return true
+			}
+			state = ccomment
+		case minus:
+			if b != '-' {
+				return true
+			}
+			state = sqlcomment
+		case ccomment:
+			if b == '*' {
+				state = endcomment
+			}
+		case sqlcomment:
+			if b == '\n' {
+				state = code
+			}
+		case endcomment:
+			switch b {
+			case '/':
+				state = code
+			case '*':
+				state = endcomment
+			default:
+				state = ccomment
+			}
+		}
+	}
+	return state == slash || state == minus
+}

driver/util_test.go

@@ -1,9 +1,13 @@
 package driver
 
 import (
+	"context"
 	"database/sql/driver"
-	"reflect"
+	"slices"
 	"testing"
+
+	_ "github.com/ncruces/go-sqlite3/embed"
+	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
 )
 
 func Test_namedValues(t *testing.T) {
@@ -12,7 +16,71 @@ func Test_namedValues(t *testing.T) {
 		{Ordinal: 2, Value: false},
 	}
 	got := namedValues([]driver.Value{true, false})
-	if !reflect.DeepEqual(got, want) {
+	if !slices.Equal(got, want) {
 		t.Errorf("got %v, want %v", got, want)
 	}
 }
+
+func Fuzz_notWhitespace(f *testing.F) {
+	f.Add("")
+	f.Add(" ")
+	f.Add(";")
+	f.Add("0")
+	f.Add("-")
+	f.Add("-0")
+	f.Add("--")
+	f.Add("--0")
+	f.Add("--\n")
+	f.Add("--0\n")
+	f.Add("/0")
+	f.Add("/*")
+	f.Add("/*/")
+	f.Add("/**")
+	f.Add("/*0")
+	f.Add("/**/")
+	f.Add("/***/")
+	f.Add("/**0/")
+	f.Add("\v")
+	f.Add(" \v")
+	f.Add("\xf0")
+	f.Add("\000")
+
+	db, err := Open(":memory:")
+	if err != nil {
+		f.Fatal(err)
+	}
+	defer db.Close()
+
+	f.Fuzz(func(t *testing.T, str string) {
+		if len(str) > 128 {
+			t.SkipNow()
+		}
+
+		c, err := db.Conn(context.Background())
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer c.Close()
+
+		c.Raw(func(driverConn any) error {
+			conn := driverConn.(*conn).Conn
+			stmt, tail, err := conn.Prepare(str)
+			stmt.Close()
+
+			// It's hard to be bug for bug compatible with SQLite.
+			// We settle for somewhat less:
+			//   - if SQLite reports whitespace, we must too
+			//   - if we report whitespace, SQLite must not parse a statement
+			if notWhitespace(str) {
+				if stmt == nil && tail == "" && err == nil {
+					t.Errorf("was whitespace: %q", str)
+				}
+			} else {
+				if stmt != nil {
+					t.Errorf("was not whitespace: %q (%v)", str, err)
+				}
+			}
+			return nil
+		})
+	})
+}

embed/README.md

@@ -1,6 +1,6 @@
 # Embeddable Wasm build of SQLite
 
-This folder includes an embeddable Wasm build of SQLite 3.46.0 for use with
+This folder includes an embeddable Wasm build of SQLite 3.49.1 for use with
 [`github.com/ncruces/go-sqlite3`](https://pkg.go.dev/github.com/ncruces/go-sqlite3).
 
 The following optional features are compiled in:
@@ -9,6 +9,7 @@ The following optional features are compiled in:
 - [JSON](https://sqlite.org/json1.html)
 - [R*Tree](https://sqlite.org/rtree.html)
 - [GeoPoly](https://sqlite.org/geopoly.html)
+- [Spellfix1](https://sqlite.org/spellfix1.html)
 - [soundex](https://sqlite.org/lang_corefunc.html#soundex)
 - [stat4](https://sqlite.org/compile.html#enable_stat4)
 - [base64](https://github.com/sqlite/sqlite/blob/master/ext/misc/base64.c)
@@ -17,14 +18,24 @@ The following optional features are compiled in:
 - [regexp](https://github.com/sqlite/sqlite/blob/master/ext/misc/regexp.c)
 - [series](https://github.com/sqlite/sqlite/blob/master/ext/misc/series.c)
 - [uint](https://github.com/sqlite/sqlite/blob/master/ext/misc/uint.c)
-- [uuid](https://github.com/sqlite/sqlite/blob/master/ext/misc/uuid.c)
 - [time](../sqlite3/time.c)
 
-See the [configuration options](../sqlite3/sqlite_cfg.h),
+See the [configuration options](../sqlite3/sqlite_opt.h),
 and [patches](../sqlite3) applied.
 
 Built using [`wasi-sdk`](https://github.com/WebAssembly/wasi-sdk),
 and [`binaryen`](https://github.com/WebAssembly/binaryen).
 
 The build is easily reproducible, and verifiable, using
-[Artifact Attestations](https://github.com/ncruces/go-sqlite3/attestations).
+[Artifact Attestations](https://github.com/ncruces/go-sqlite3/attestations).
+
+### Customizing the build
+
+You can use your own custom build of SQLite.
+
+Examples of custom builds of SQLite are:
+- [`github.com/ncruces/go-sqlite3/embed/bcw2`](https://github.com/ncruces/go-sqlite3/tree/main/embed/bcw2)
+  built from a branch supporting [`BEGIN CONCURRENT`](https://sqlite.org/src/doc/begin-concurrent/doc/begin_concurrent.md)
+  and [Wal2](https://sqlite.org/cgi/src/doc/wal2/doc/wal2.md).
+- [`github.com/asg017/sqlite-vec-go-bindings/ncruces`](https://github.com/asg017/sqlite-vec-go-bindings)
+  which includes the [`sqlite-vec`](https://github.com/asg017/sqlite-vec) vector search extension.

embed/bcw2/.gitignore

@@ -0,0 +1,2 @@
+build/
+sqlite/

embed/bcw2/README.md

@@ -0,0 +1,22 @@
+# Embeddable Wasm build of SQLite
+
+This folder includes an alternative embeddable Wasm build of SQLite,
+which includes the experimental
+[`BEGIN CONCURRENT`](https://sqlite.org/src/doc/begin-concurrent/doc/begin_concurrent.md) and
+[Wal2](https://sqlite.org/cgi/src/doc/wal2/doc/wal2.md) patches.
+
+It also enables the optional
+[`UPDATE … ORDER BY … LIMIT`](https://sqlite.org/lang_update.html#optional_limit_and_order_by_clauses) and
+[`DELETE … ORDER BY … LIMIT`](https://sqlite.org/lang_delete.html#optional_limit_and_order_by_clauses) clauses,
+and the [`WITHIN GROUP ORDER BY`](https://sqlite.org/compile.html#enable_ordered_set_aggregates) aggregate syntax.
+
+> [!IMPORTANT]  
+> This package is experimental.
+> It is built from the `bedrock` branch of SQLite,
+> since that is _currently_ the most stable, maintained branch to include these features.
+
+> [!CAUTION]
+> The Wal2 journaling mode creates databases that other versions of SQLite cannot access.
+
+The build is easily reproducible, and verifiable, using
+[Artifact Attestations](https://github.com/ncruces/go-sqlite3/attestations).

embed/bcw2/bcw2_test.go

@@ -0,0 +1,59 @@
+package bcw2
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/ncruces/go-sqlite3/driver"
+	"github.com/ncruces/go-sqlite3/ext/stats"
+	"github.com/ncruces/go-sqlite3/vfs"
+)
+
+func Test_bcw2(t *testing.T) {
+	if !vfs.SupportsSharedMemory {
+		t.Skip("skipping without shared memory")
+	}
+
+	tmp := filepath.ToSlash(filepath.Join(t.TempDir(), "test.db"))
+
+	db, err := driver.Open("file:"+tmp+"?_pragma=journal_mode(wal2)&_txlock=concurrent", stats.Register)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer tx.Rollback()
+
+	_, err = tx.Exec(`CREATE TABLE test (col)`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = tx.Exec(`DELETE FROM test LIMIT 1`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = tx.Exec(`SELECT median() WITHIN GROUP (ORDER BY col) FROM test`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = tx.Commit()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var version string
+	err = db.QueryRow(`SELECT sqlite_version()`).Scan(&version)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if version != "3.50.0" {
+		t.Error(version)
+	}
+}

embed/bcw2/build.sh

@@ -0,0 +1,66 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+cd -P -- "$(dirname -- "$0")"
+
+ROOT=../../
+BINARYEN="$ROOT/tools/binaryen/bin"
+WASI_SDK="$ROOT/tools/wasi-sdk/bin"
+
+trap 'rm -rf build/ sqlite/ bcw2.tmp' EXIT
+
+mkdir -p build/ext/
+cp "$ROOT"/sqlite3/*.[ch] build/
+cp "$ROOT"/sqlite3/*.patch build/
+
+# https://sqlite.org/src/info/c09656c62155a6e8
+curl -# https://sqlite.org/src/tarball/sqlite.tar.gz?r=c09656c6 | tar xz
+
+cd sqlite
+if [[ "$OSTYPE" == "msys" || "$OSTYPE" == "cygwin" ]]; then
+	MSYS_NO_PATHCONV=1 nmake /f makefile.msc sqlite3.c "OPTS=-DSQLITE_ENABLE_UPDATE_DELETE_LIMIT -DSQLITE_ENABLE_ORDERED_SET_AGGREGATES"
+else
+	sh configure --enable-update-limit
+	OPTS=-DSQLITE_ENABLE_ORDERED_SET_AGGREGATES make sqlite3.c
+fi
+cd ~-
+
+mv sqlite/sqlite3.c             build/
+mv sqlite/sqlite3.h             build/
+mv sqlite/sqlite3ext.h          build/
+mv sqlite/ext/misc/anycollseq.c build/ext/
+mv sqlite/ext/misc/base64.c     build/ext/
+mv sqlite/ext/misc/decimal.c    build/ext/
+mv sqlite/ext/misc/ieee754.c    build/ext/
+mv sqlite/ext/misc/regexp.c     build/ext/
+mv sqlite/ext/misc/series.c     build/ext/
+mv sqlite/ext/misc/spellfix.c   build/ext/
+mv sqlite/ext/misc/uint.c       build/ext/
+
+cd build
+cat *.patch | patch -p0 --no-backup-if-mismatch
+cd ~-
+
+"$WASI_SDK/clang" --target=wasm32-wasi -std=c23 -g0 -O2 \
+	-Wall -Wextra -Wno-unused-parameter -Wno-unused-function \
+	-o bcw2.wasm "build/main.c" \
+	-I"build" \
+	-mexec-model=reactor \
+	-msimd128 -mmutable-globals -mmultivalue \
+	-mbulk-memory -mreference-types \
+	-mnontrapping-fptoint -msign-ext \
+	-fno-stack-protector -fno-stack-clash-protection \
+	-Wl,--stack-first \
+	-Wl,--import-undefined \
+	-Wl,--initial-memory=327680 \
+	-D_HAVE_SQLITE_CONFIG_H \
+	-DSQLITE_ENABLE_UPDATE_DELETE_LIMIT \
+	-DSQLITE_CUSTOM_INCLUDE=sqlite_opt.h \
+	$(awk '{print "-Wl,--export="$0}' ../exports.txt)
+
+"$BINARYEN/wasm-ctor-eval" -g -c _initialize bcw2.wasm -o bcw2.tmp
+"$BINARYEN/wasm-opt" -g --strip --strip-producers -c -O3 \
+	bcw2.tmp -o bcw2.wasm \
+	--enable-simd --enable-mutable-globals --enable-multivalue \
+	--enable-bulk-memory --enable-reference-types \
+	--enable-nontrapping-float-to-int --enable-sign-ext

embed/bcw2/go.mod

@@ -0,0 +1,14 @@
+module github.com/ncruces/go-sqlite3/embed/bcw2
+
+go 1.22.0
+
+toolchain go1.24.0
+
+require github.com/ncruces/go-sqlite3 v0.23.1
+
+require (
+	github.com/ncruces/julianday v1.0.0 // indirect
+	github.com/ncruces/sort v0.1.5 // indirect
+	github.com/tetratelabs/wazero v1.9.0 // indirect
+	golang.org/x/sys v0.30.0 // indirect
+)

embed/bcw2/go.sum

@@ -0,0 +1,12 @@
+github.com/ncruces/go-sqlite3 v0.23.1 h1:zGAd76q+Tr18z/xKGatUlzBQdjR3J+rexfANUcjAgkY=
+github.com/ncruces/go-sqlite3 v0.23.1/go.mod h1:Xg3FyAZl25HcBSFmcbymdfoTqD7jRnBUmv1jSrbIjdE=
+github.com/ncruces/julianday v1.0.0 h1:fH0OKwa7NWvniGQtxdJRxAgkBMolni2BjDHaWTxqt7M=
+github.com/ncruces/julianday v1.0.0/go.mod h1:Dusn2KvZrrovOMJuOt0TNXL6tB7U2E8kvza5fFc9G7g=
+github.com/ncruces/sort v0.1.5 h1:fiFWXXAqKI8QckPf/6hu/bGFwcEPrirIOFaJqWujs4k=
+github.com/ncruces/sort v0.1.5/go.mod h1:obJToO4rYr6VWP0Uw5FYymgYGt3Br4RXcs/JdKaXAPk=
+github.com/tetratelabs/wazero v1.9.0 h1:IcZ56OuxrtaEz8UYNRHBrUa9bYeX9oVY93KspZZBf/I=
+github.com/tetratelabs/wazero v1.9.0/go.mod h1:TSbcXCfFP0L2FGkRPxHphadXPjo1T6W+CseNNY7EkjM=
+golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
+golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/text v0.22.0 h1:bofq7m3/HAFvbF51jz3Q9wLg3jkvSPuiZu/pD1XwgtM=
+golang.org/x/text v0.22.0/go.mod h1:YRoo4H8PVmsu+E3Ou7cqLVH8oXWIHVoX0jqUWALQhfY=

embed/bcw2/init.go

@@ -0,0 +1,24 @@
+// Package bcw2 embeds SQLite into your application.
+//
+// Importing package bcw2 initializes the [sqlite3.Binary] variable
+// with a build of SQLite that includes the [BEGIN CONCURRENT] and [Wal2] patches:
+//
+//	import _ "github.com/ncruces/go-sqlite3/embed/bcw2"
+//
+// [BEGIN CONCURRENT]: https://sqlite.org/src/doc/begin-concurrent/doc/begin_concurrent.md
+// [Wal2]: https://sqlite.org/cgi/src/doc/wal2/doc/wal2.md
+package bcw2
+
+import (
+	_ "embed"
+	"unsafe"
+
+	"github.com/ncruces/go-sqlite3"
+)
+
+//go:embed bcw2.wasm
+var binary string
+
+func init() {
+	sqlite3.Binary = unsafe.Slice(unsafe.StringData(binary), len(binary))
+}

embed/build.sh

@@ -4,26 +4,27 @@ set -euo pipefail
 cd -P -- "$(dirname -- "$0")"
 
 ROOT=../
-BINARYEN="$ROOT/tools/binaryen-version_117/bin"
-WASI_SDK="$ROOT/tools/wasi-sdk-22.0/bin"
+BINARYEN="$ROOT/tools/binaryen/bin"
+WASI_SDK="$ROOT/tools/wasi-sdk/bin"
 
-"$WASI_SDK/clang" --target=wasm32-wasi -std=c17 -flto -g0 -O2 \
+trap 'rm -f sqlite3.tmp' EXIT
+
+"$WASI_SDK/clang" --target=wasm32-wasi -std=c23 -g0 -O2 \
 	-Wall -Wextra -Wno-unused-parameter -Wno-unused-function \
 	-o sqlite3.wasm "$ROOT/sqlite3/main.c" \
 	-I"$ROOT/sqlite3" \
 	-mexec-model=reactor \
-	-msimd128 -mmutable-globals \
+	-msimd128 -mmutable-globals -mmultivalue \
 	-mbulk-memory -mreference-types \
 	-mnontrapping-fptoint -msign-ext \
 	-fno-stack-protector -fno-stack-clash-protection \
-	-Wl,--initial-memory=327680 \
 	-Wl,--stack-first \
 	-Wl,--import-undefined \
+	-Wl,--initial-memory=327680 \
 	-D_HAVE_SQLITE_CONFIG_H \
 	-DSQLITE_CUSTOM_INCLUDE=sqlite_opt.h \
 	$(awk '{print "-Wl,--export="$0}' exports.txt)
 
-trap 'rm -f sqlite3.tmp' EXIT
 "$BINARYEN/wasm-ctor-eval" -g -c _initialize sqlite3.wasm -o sqlite3.tmp
 "$BINARYEN/wasm-opt" -g --strip --strip-producers -c -O3 \
 	sqlite3.tmp -o sqlite3.wasm \

embed/exports.txt

@@ -1,7 +1,4 @@
 aligned_alloc
-free
-malloc
-malloc_destructor
 sqlite3_anycollseq_init
 sqlite3_autovacuum_pages_go
 sqlite3_backup_finish
@@ -9,7 +6,7 @@ sqlite3_backup_init
 sqlite3_backup_pagecount
 sqlite3_backup_remaining
 sqlite3_backup_step
-sqlite3_bind_blob64
+sqlite3_bind_blob_go
 sqlite3_bind_double
 sqlite3_bind_int64
 sqlite3_bind_null
@@ -17,7 +14,7 @@ sqlite3_bind_parameter_count
 sqlite3_bind_parameter_index
 sqlite3_bind_parameter_name
 sqlite3_bind_pointer_go
-sqlite3_bind_text64
+sqlite3_bind_text_go
 sqlite3_bind_value
 sqlite3_bind_zeroblob64
 sqlite3_blob_bytes
@@ -54,33 +51,43 @@ sqlite3_create_collation_go
 sqlite3_create_function_go
 sqlite3_create_module_go
 sqlite3_create_window_function_go
+sqlite3_data_count
 sqlite3_database_file_object
+sqlite3_db_cacheflush
 sqlite3_db_config
 sqlite3_db_filename
 sqlite3_db_name
 sqlite3_db_readonly
 sqlite3_db_release_memory
+sqlite3_db_status
 sqlite3_declare_vtab
 sqlite3_errcode
 sqlite3_errmsg
 sqlite3_error_offset
 sqlite3_errstr
 sqlite3_exec
+sqlite3_expanded_sql
+sqlite3_file_control
 sqlite3_filename_database
 sqlite3_filename_journal
 sqlite3_filename_wal
 sqlite3_finalize
+sqlite3_free
 sqlite3_get_autocommit
 sqlite3_get_auxdata
+sqlite3_hard_heap_limit64
 sqlite3_interrupt
+sqlite3_invoke_busy_handler_go
 sqlite3_last_insert_rowid
 sqlite3_limit
+sqlite3_malloc64
 sqlite3_open_v2
 sqlite3_overload_function
 sqlite3_prepare_v3
 sqlite3_progress_handler_go
+sqlite3_realloc64
 sqlite3_reset
-sqlite3_result_blob64
+sqlite3_result_blob_go
 sqlite3_result_double
 sqlite3_result_error
 sqlite3_result_error_code
@@ -89,27 +96,30 @@ sqlite3_result_error_toobig
 sqlite3_result_int64
 sqlite3_result_null
 sqlite3_result_pointer_go
-sqlite3_result_text64
+sqlite3_result_text_go
 sqlite3_result_value
 sqlite3_result_zeroblob64
 sqlite3_rollback_hook_go
 sqlite3_set_authorizer_go
 sqlite3_set_auxdata_go
 sqlite3_set_last_insert_rowid
+sqlite3_soft_heap_limit64
 sqlite3_step
 sqlite3_stmt_busy
 sqlite3_stmt_readonly
 sqlite3_stmt_status
+sqlite3_table_column_metadata
 sqlite3_total_changes64
+sqlite3_trace_go
 sqlite3_txn_state
 sqlite3_update_hook_go
 sqlite3_uri_key
-sqlite3_uri_parameter
 sqlite3_value_blob
 sqlite3_value_bytes
 sqlite3_value_double
 sqlite3_value_dup
 sqlite3_value_free
+sqlite3_value_frombind
 sqlite3_value_int64
 sqlite3_value_nochange
 sqlite3_value_numeric_type

embed/init.go

@@ -8,13 +8,14 @@ package embed
 
 import (
 	_ "embed"
+	"unsafe"
 
 	"github.com/ncruces/go-sqlite3"
 )
 
 //go:embed sqlite3.wasm
-var binary []byte
+var binary string
 
 func init() {
-	sqlite3.Binary = binary
+	sqlite3.Binary = unsafe.Slice(unsafe.StringData(binary), len(binary))
 }

embed/init_test.go

@@ -0,0 +1,25 @@
+package embed
+
+import (
+	"testing"
+
+	"github.com/ncruces/go-sqlite3/driver"
+	_ "github.com/ncruces/go-sqlite3/vfs/memdb"
+)
+
+func Test_init(t *testing.T) {
+	db, err := driver.Open("file:/test.db?vfs=memdb")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	var version string
+	err = db.QueryRow(`SELECT sqlite_version()`).Scan(&version)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if version != "3.49.1" {
+		t.Error(version)
+	}
+}

error.go

@@ -15,7 +15,7 @@ type Error struct {
 	str  string
 	msg  string
 	sql  string
-	code uint64
+	code res_t
 }
 
 // Code returns the primary error code for this error.
@@ -106,6 +106,11 @@ func (e ErrorCode) Temporary() bool {
 	return e == BUSY
 }
 
+// ExtendedCode returns the extended error code for this error.
+func (e ErrorCode) ExtendedCode() ExtendedErrorCode {
+	return ExtendedErrorCode(e)
+}
+
 // Error implements the error interface.
 func (e ExtendedErrorCode) Error() string {
 	return util.ErrorCodeString(uint32(e))
@@ -136,27 +141,32 @@ func (e ExtendedErrorCode) Timeout() bool {
 	return e == BUSY_TIMEOUT
 }
 
-func errorCode(err error, def ErrorCode) (msg string, code uint32) {
+// Code returns the primary error code for this error.
+func (e ExtendedErrorCode) Code() ErrorCode {
+	return ErrorCode(e)
+}
+
+func errorCode(err error, def ErrorCode) (msg string, code res_t) {
 	switch code := err.(type) {
 	case nil:
 		return "", _OK
 	case ErrorCode:
-		return "", uint32(code)
+		return "", res_t(code)
 	case xErrorCode:
-		return "", uint32(code)
+		return "", res_t(code)
 	case *Error:
-		return code.msg, uint32(code.code)
+		return code.msg, res_t(code.code)
 	}
 
 	var ecode ErrorCode
 	var xcode xErrorCode
 	switch {
 	case errors.As(err, &xcode):
-		code = uint32(xcode)
+		code = res_t(xcode)
 	case errors.As(err, &ecode):
-		code = uint32(ecode)
+		code = res_t(ecode)
 	default:
-		code = uint32(def)
+		code = res_t(def)
 	}
 	return err.Error(), code
 }

error_test.go

@@ -2,6 +2,7 @@ package sqlite3
 
 import (
 	"errors"
+	"fmt"
 	"strings"
 	"testing"
 
@@ -10,7 +11,7 @@ import (
 
 func Test_assertErr(t *testing.T) {
 	err := util.AssertErr()
-	if s := err.Error(); !strings.HasPrefix(s, "sqlite3: assertion failed") || !strings.HasSuffix(s, "error_test.go:12)") {
+	if s := err.Error(); !strings.HasPrefix(s, "sqlite3: assertion failed") || !strings.HasSuffix(s, "error_test.go:13)") {
 		t.Errorf("got %q", s)
 	}
 }
@@ -58,14 +59,14 @@ func TestError_Temporary(t *testing.T) {
 
 	tests := []struct {
 		name string
-		code uint64
+		code res_t
 		want bool
 	}{
-		{"ERROR", uint64(ERROR), false},
-		{"BUSY", uint64(BUSY), true},
-		{"BUSY_RECOVERY", uint64(BUSY_RECOVERY), true},
-		{"BUSY_SNAPSHOT", uint64(BUSY_SNAPSHOT), true},
-		{"BUSY_TIMEOUT", uint64(BUSY_TIMEOUT), true},
+		{"ERROR", res_t(ERROR), false},
+		{"BUSY", res_t(BUSY), true},
+		{"BUSY_RECOVERY", res_t(BUSY_RECOVERY), true},
+		{"BUSY_SNAPSHOT", res_t(BUSY_SNAPSHOT), true},
+		{"BUSY_TIMEOUT", res_t(BUSY_TIMEOUT), true},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -96,14 +97,14 @@ func TestError_Timeout(t *testing.T) {
 
 	tests := []struct {
 		name string
-		code uint64
+		code res_t
 		want bool
 	}{
-		{"ERROR", uint64(ERROR), false},
-		{"BUSY", uint64(BUSY), false},
-		{"BUSY_RECOVERY", uint64(BUSY_RECOVERY), false},
-		{"BUSY_SNAPSHOT", uint64(BUSY_SNAPSHOT), false},
-		{"BUSY_TIMEOUT", uint64(BUSY_TIMEOUT), true},
+		{"ERROR", res_t(ERROR), false},
+		{"BUSY", res_t(BUSY), false},
+		{"BUSY_RECOVERY", res_t(BUSY_RECOVERY), false},
+		{"BUSY_SNAPSHOT", res_t(BUSY_SNAPSHOT), false},
+		{"BUSY_TIMEOUT", res_t(BUSY_TIMEOUT), true},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -135,8 +136,8 @@ func Test_ErrorCode_Error(t *testing.T) {
 	// Test all error codes.
 	for i := 0; i == int(ErrorCode(i)); i++ {
 		want := "sqlite3: "
-		r := db.call("sqlite3_errstr", uint64(i))
-		want += util.ReadString(db.mod, uint32(r), _MAX_NAME)
+		ptr := ptr_t(db.call("sqlite3_errstr", stk_t(i)))
+		want += util.ReadString(db.mod, ptr, _MAX_NAME)
 
 		got := ErrorCode(i).Error()
 		if got != want {
@@ -157,8 +158,8 @@ func Test_ExtendedErrorCode_Error(t *testing.T) {
 	// Test all extended error codes.
 	for i := 0; i == int(ExtendedErrorCode(i)); i++ {
 		want := "sqlite3: "
-		r := db.call("sqlite3_errstr", uint64(i))
-		want += util.ReadString(db.mod, uint32(r), _MAX_NAME)
+		ptr := ptr_t(db.call("sqlite3_errstr", stk_t(i)))
+		want += util.ReadString(db.mod, ptr, _MAX_NAME)
 
 		got := ExtendedErrorCode(i).Error()
 		if got != want {
@@ -166,3 +167,32 @@ func Test_ExtendedErrorCode_Error(t *testing.T) {
 		}
 	}
 }
+
+func Test_errorCode(t *testing.T) {
+	tests := []struct {
+		arg      error
+		wantMsg  string
+		wantCode res_t
+	}{
+		{nil, "", _OK},
+		{ERROR, "", util.ERROR},
+		{IOERR, "", util.IOERR},
+		{IOERR_READ, "", util.IOERR_READ},
+		{&Error{code: util.ERROR}, "", util.ERROR},
+		{fmt.Errorf("%w", ERROR), ERROR.Error(), util.ERROR},
+		{fmt.Errorf("%w", IOERR), IOERR.Error(), util.IOERR},
+		{fmt.Errorf("%w", IOERR_READ), IOERR_READ.Error(), util.IOERR_READ},
+		{fmt.Errorf("error"), "error", util.ERROR},
+	}
+	for _, tt := range tests {
+		t.Run("", func(t *testing.T) {
+			gotMsg, gotCode := errorCode(tt.arg, ERROR)
+			if gotMsg != tt.wantMsg {
+				t.Errorf("errorCode() gotMsg = %q, want %q", gotMsg, tt.wantMsg)
+			}
+			if gotCode != tt.wantCode {
+				t.Errorf("errorCode() gotCode = %d, want %d", gotCode, tt.wantCode)
+			}
+		})
+	}
+}

ext/README.md

@@ -0,0 +1,48 @@
+# Go SQLite Extensions
+
+This folder collects optional SQLite extensions
+you can load into your database connections.
+
+### Extensions
+
+- [`github.com/ncruces/go-sqlite3/ext/array`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/array)
+  provides the [`array`](https://sqlite.org/carray.html) table-valued function.
+- [`github.com/ncruces/go-sqlite3/ext/blobio`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/blobio)
+  simplifies [incremental BLOB I/O](https://sqlite.org/c3ref/blob_open.html).
+- [`github.com/ncruces/go-sqlite3/ext/bloom`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/bloom)
+  provides a [Bloom filter](https://github.com/nalgeon/sqlean/issues/27#issuecomment-1002267134) virtual table.
+- [`github.com/ncruces/go-sqlite3/ext/closure`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/closure)
+  provides a transitive closure virtual table.
+- [`github.com/ncruces/go-sqlite3/ext/csv`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/csv)
+  reads [comma-separated values](https://sqlite.org/csv.html).
+- [`github.com/ncruces/go-sqlite3/ext/fileio`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/fileio)
+  reads, writes and lists files.
+- [`github.com/ncruces/go-sqlite3/ext/hash`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/hash)
+  provides cryptographic hash functions.
+- [`github.com/ncruces/go-sqlite3/ext/lines`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/lines)
+  reads data [line-by-line](https://github.com/asg017/sqlite-lines).
+- [`github.com/ncruces/go-sqlite3/ext/pivot`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/pivot)
+  creates [pivot tables](https://github.com/jakethaw/pivot_vtab).
+- [`github.com/ncruces/go-sqlite3/ext/regexp`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/regexp)
+  provides regular expression functions.
+- [`github.com/ncruces/go-sqlite3/ext/serdes`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/serdes)
+  (de)serializes databases.
+- [`github.com/ncruces/go-sqlite3/ext/statement`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/statement)
+  creates [parameterized views](https://github.com/0x09/sqlite-statement-vtab).
+- [`github.com/ncruces/go-sqlite3/ext/stats`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/stats)
+  provides [statistics](https://www.oreilly.com/library/view/sql-in-a/9780596155322/ch04s02.html) functions.
+- [`github.com/ncruces/go-sqlite3/ext/unicode`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/unicode)
+  provides [Unicode aware](https://sqlite.org/src/dir/ext/icu) functions.
+- [`github.com/ncruces/go-sqlite3/ext/uuid`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/uuid)
+  generates [UUIDs](https://en.wikipedia.org/wiki/Universally_unique_identifier).
+- [`github.com/ncruces/go-sqlite3/ext/zorder`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/zorder)
+  maps multidimensional data to one dimension.
+
+### Pakages
+
+These packages may also be useful to work with SQLite:
+
+- [`github.com/ncruces/decimal`](https://pkg.go.dev/github.com/ncruces/decimal)
+  decimal arithmetic.
+- [`github.com/ncruces/julianday`](https://pkg.go.dev/github.com/ncruces/julianday)
+  Julian day math.

ext/array/array.go

@@ -15,8 +15,8 @@ import (
 // The argument must be bound to a Go slice or array of
 // ints, floats, bools, strings or byte slices,
 // using [sqlite3.BindPointer] or [sqlite3.Pointer].
-func Register(db *sqlite3.Conn) {
-	sqlite3.CreateModule(db, "array", nil,
+func Register(db *sqlite3.Conn) error {
+	return sqlite3.CreateModule(db, "array", nil,
 		func(db *sqlite3.Conn, _, _, _ string, _ ...string) (array, error) {
 			err := db.DeclareVTab(`CREATE TABLE x(value, array HIDDEN)`)
 			return array{}, err
@@ -62,7 +62,7 @@ func (c *cursor) RowID() (int64, error) {
 	return int64(c.rowID), nil
 }
 
-func (c *cursor) Column(ctx *sqlite3.Context, n int) error {
+func (c *cursor) Column(ctx sqlite3.Context, n int) error {
 	if n != 0 {
 		return nil
 	}

ext/array/array_test.go

@@ -12,13 +12,11 @@ import (
 	_ "github.com/ncruces/go-sqlite3/embed"
 	"github.com/ncruces/go-sqlite3/ext/array"
 	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
+	"github.com/ncruces/go-sqlite3/vfs/memdb"
 )
 
 func Example_driver() {
-	db, err := driver.Open(":memory:", func(c *sqlite3.Conn) error {
-		array.Register(c)
-		return nil
-	})
+	db, err := driver.Open("file:/test.db?vfs=memdb", array.Register)
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -53,14 +51,14 @@ func Example_driver() {
 }
 
 func Example() {
+	sqlite3.AutoExtension(array.Register)
+
 	db, err := sqlite3.Open(":memory:")
 	if err != nil {
 		log.Fatal(err)
 	}
 	defer db.Close()
 
-	array.Register(db)
-
 	stmt, _, err := db.Prepare(`
 		SELECT name
 		FROM pragma_function_list
@@ -90,11 +88,9 @@ func Example() {
 
 func Test_cursor_Column(t *testing.T) {
 	t.Parallel()
+	tmp := memdb.TestDB(t)
 
-	db, err := driver.Open(":memory:", func(c *sqlite3.Conn) error {
-		array.Register(c)
-		return nil
-	})
+	db, err := driver.Open(tmp, array.Register)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -126,7 +122,7 @@ func Test_cursor_Column(t *testing.T) {
 		want = want[1:]
 	}
 	if err := rows.Err(); err != nil {
-		log.Fatal(err)
+		t.Fatal(err)
 	}
 }
 
@@ -139,7 +135,10 @@ func Test_array_errors(t *testing.T) {
 	}
 	defer db.Close()
 
-	array.Register(db)
+	err = array.Register(db)
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	err = db.Exec(`SELECT * FROM array()`)
 	if err == nil {

ext/blobio/blob.go

@@ -11,11 +11,11 @@ import (
 
 // Register registers the SQL functions:
 //
-//	readblob(schema, table, column, rowid, offset, n)
+//	readblob(schema, table, column, rowid, offset, n/writer)
 //
 // Reads n bytes of a blob, starting at offset.
 //
-//	writeblob(schema, table, column, rowid, offset, data)
+//	writeblob(schema, table, column, rowid, offset, data/reader)
 //
 // Writes data into a blob, at the given offset.
 //
@@ -27,63 +27,83 @@ import (
 // using [sqlite3.BindPointer] or [sqlite3.Pointer].
 // The optional args will be passed to the callback,
 // along with the [sqlite3.Blob] handle.
+// The [sqlite3.Blob] handle is only valid during
+// the execution of the callback. Callers cannot
+// read or write to the handle after the callback
+// exits.
 //
 // https://sqlite.org/c3ref/blob.html
-func Register(db *sqlite3.Conn) {
-	db.CreateFunction("readblob", 6, 0, readblob)
-	db.CreateFunction("writeblob", 6, 0, writeblob)
-	db.CreateFunction("openblob", -1, 0, openblob)
+func Register(db *sqlite3.Conn) error {
+	return errors.Join(
+		db.CreateFunction("readblob", 6, 0, readblob),
+		db.CreateFunction("writeblob", 6, 0, writeblob),
+		db.CreateFunction("openblob", -1, 0, openblob))
 }
 
 // OpenCallback is the type for the openblob callback.
 type OpenCallback func(*sqlite3.Blob, ...sqlite3.Value) error
 
 func readblob(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	_ = arg[5] // bounds check
+
 	blob, err := getAuxBlob(ctx, arg, false)
 	if err != nil {
 		ctx.ResultError(err)
-		return
+		return // notest
 	}
 
 	_, err = blob.Seek(arg[4].Int64(), io.SeekStart)
 	if err != nil {
 		ctx.ResultError(err)
-		return
+		return // notest
 	}
 
-	n := arg[5].Int64()
-	if n <= 0 {
-		return
+	if p, ok := arg[5].Pointer().(io.Writer); ok {
+		var n int64
+		n, err = blob.WriteTo(p)
+		ctx.ResultInt64(n)
+	} else {
+		n := arg[5].Int64()
+		if n <= 0 {
+			return
+		}
+		buf := make([]byte, n)
+		_, err = io.ReadFull(blob, buf)
+		ctx.ResultBlob(buf)
 	}
-	buf := make([]byte, n)
-
-	_, err = io.ReadFull(blob, buf)
 	if err != nil {
 		ctx.ResultError(err)
-		return
+		return // notest
 	}
 
-	ctx.ResultBlob(buf)
 	setAuxBlob(ctx, blob, false)
 }
 
 func writeblob(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	_ = arg[5] // bounds check
+
 	blob, err := getAuxBlob(ctx, arg, true)
 	if err != nil {
 		ctx.ResultError(err)
-		return
+		return // notest
 	}
 
 	_, err = blob.Seek(arg[4].Int64(), io.SeekStart)
 	if err != nil {
 		ctx.ResultError(err)
-		return
+		return // notest
 	}
 
-	_, err = blob.Write(arg[5].RawBlob())
+	if p, ok := arg[5].Pointer().(io.Reader); ok {
+		var n int64
+		n, err = blob.ReadFrom(p)
+		ctx.ResultInt64(n)
+	} else {
+		_, err = blob.Write(arg[5].RawBlob())
+	}
 	if err != nil {
 		ctx.ResultError(err)
-		return
+		return // notest
 	}
 
 	setAuxBlob(ctx, blob, false)
@@ -98,14 +118,14 @@ func openblob(ctx sqlite3.Context, arg ...sqlite3.Value) {
 	blob, err := getAuxBlob(ctx, arg, arg[4].Bool())
 	if err != nil {
 		ctx.ResultError(err)
-		return
+		return // notest
 	}
 
 	fn := arg[5].Pointer().(OpenCallback)
 	err = fn(blob, arg[6:]...)
 	if err != nil {
 		ctx.ResultError(err)
-		return
+		return // notest
 	}
 
 	setAuxBlob(ctx, blob, true)

ext/blobio/blob_test.go

@@ -4,7 +4,8 @@ import (
 	"io"
 	"log"
 	"os"
-	"reflect"
+	"slices"
+	"strings"
 	"testing"
 
 	"github.com/ncruces/go-sqlite3"
@@ -18,10 +19,7 @@ import (
 
 func Example() {
 	// Open the database, registering the extension.
-	db, err := driver.Open("file:/test.db?vfs=memdb", func(conn *sqlite3.Conn) error {
-		blobio.Register(conn)
-		return nil
-	})
+	db, err := driver.Open("file:/test.db?vfs=memdb", blobio.Register)
 
 	if err != nil {
 		log.Fatal(err)
@@ -36,23 +34,26 @@ func Example() {
 	const message = "Hello BLOB!"
 
 	// Create the BLOB.
-	_, err = db.Exec(`INSERT INTO test VALUES (?)`, sqlite3.ZeroBlob(len(message)))
+	r, err := db.Exec(`INSERT INTO test VALUES (?)`, sqlite3.ZeroBlob(len(message)))
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	id, err := r.LastInsertId()
 	if err != nil {
 		log.Fatal(err)
 	}
 
 	// Write the BLOB.
-	_, err = db.Exec(`SELECT writeblob('main', 'test', 'col', last_insert_rowid(), 0, ?)`, message)
+	_, err = db.Exec(`SELECT writeblob('main', 'test', 'col', ?, 0, ?)`,
+		id, message)
 	if err != nil {
 		log.Fatal(err)
 	}
 
 	// Read the BLOB.
-	_, err = db.Exec(`SELECT openblob('main', 'test', 'col', rowid, false, ?) FROM test`,
-		sqlite3.Pointer[blobio.OpenCallback](func(blob *sqlite3.Blob, _ ...sqlite3.Value) error {
-			_, err = io.Copy(os.Stdout, blob)
-			return err
-		}))
+	_, err = db.Exec(`SELECT readblob('main', 'test', 'col', ?, 0, ?)`,
+		id, sqlite3.Pointer(os.Stdout))
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -60,6 +61,12 @@ func Example() {
 	// Hello BLOB!
 }
 
+func TestMain(m *testing.M) {
+	sqlite3.AutoExtension(blobio.Register)
+	sqlite3.AutoExtension(array.Register)
+	m.Run()
+}
+
 func Test_readblob(t *testing.T) {
 	t.Parallel()
 
@@ -69,9 +76,6 @@ func Test_readblob(t *testing.T) {
 	}
 	defer db.Close()
 
-	blobio.Register(db)
-	array.Register(db)
-
 	err = db.Exec(`SELECT readblob()`)
 	if err == nil {
 		t.Fatal("want error")
@@ -79,44 +83,135 @@ func Test_readblob(t *testing.T) {
 		t.Log(err)
 	}
 
+	err = db.Exec(`SELECT readblob('main', 'test1', 'col', 1, 1, 1)`)
+	if err == nil {
+		t.Fatal("want error")
+	} else {
+		t.Log(err)
+	}
+
 	err = db.Exec(`
 		CREATE TABLE test1 (col);
 		CREATE TABLE test2 (col);
 		INSERT INTO test1 VALUES (x'cafe');
+		INSERT INTO test1 VALUES (x'dead');
 		INSERT INTO test2 VALUES (x'babe');
 	`)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	stmt, _, err := db.Prepare(`SELECT readblob('main', value, 'col', 1, 1, 1) FROM array(?)`)
+	err = db.Exec(`SELECT readblob('main', 'test1', 'col', 1, -1, 1)`)
+	if err == nil {
+		t.Fatal("want error")
+	} else {
+		t.Log(err)
+	}
+
+	err = db.Exec(`SELECT readblob('main', 'test1', 'col', 1, 1, 0)`)
+	if err != nil {
+		t.Log(err)
+	}
+
+	tests := []struct {
+		name  string
+		sql   string
+		want1 string
+		want2 string
+	}{
+		{"rows", `SELECT readblob('main', 'test1', 'col', rowid, 1, 1) FROM test1`, "\xfe", "\xad"},
+		{"tables", `SELECT readblob('main', value, 'col', 1, 1, 1) FROM array(?)`, "\xfe", "\xbe"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			stmt, _, err := db.Prepare(tt.sql)
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer stmt.Close()
+
+			if stmt.BindCount() == 1 {
+				err = stmt.BindPointer(1, []string{"test1", "test2"})
+				if err != nil {
+					t.Fatal(err)
+				}
+			}
+
+			if stmt.Step() {
+				got := stmt.ColumnText(0)
+				if got != tt.want1 {
+					t.Errorf("got %q", got)
+				}
+			}
+
+			if stmt.Step() {
+				got := stmt.ColumnText(0)
+				if got != tt.want2 {
+					t.Errorf("got %q", got)
+				}
+			}
+
+			err = stmt.Err()
+			if err != nil {
+				t.Fatal(err)
+			}
+		})
+	}
+}
+
+func Test_writeblob(t *testing.T) {
+	t.Parallel()
+
+	db, err := sqlite3.Open(":memory:")
 	if err != nil {
 		t.Fatal(err)
 	}
+	defer db.Close()
+
+	err = db.Exec(`SELECT writeblob()`)
+	if err == nil {
+		t.Fatal("want error")
+	} else {
+		t.Log(err)
+	}
+
+	err = db.Exec(`SELECT writeblob('main', 'test', 'col', 1, 1, x'')`)
+	if err == nil {
+		t.Fatal("want error")
+	} else {
+		t.Log(err)
+	}
+
+	err = db.Exec(`
+		CREATE TABLE test (col);
+		INSERT INTO test VALUES (x'cafe');
+	`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = db.Exec(`SELECT writeblob('main', 'test', 'col', 1, -1, x'')`)
+	if err == nil {
+		t.Fatal("want error")
+	} else {
+		t.Log(err)
+	}
+
+	stmt, _, err := db.Prepare(`SELECT writeblob('main', 'test', 'col', 1, 0, ?)`)
+	if err != nil {
+		t.Log(err)
+	}
 	defer stmt.Close()
 
-	err = stmt.BindPointer(1, []string{"test1", "test2"})
+	err = stmt.BindPointer(1, strings.NewReader("\xba\xbe"))
 	if err != nil {
-		t.Fatal(err)
+		t.Log(err)
 	}
 
-	if stmt.Step() {
-		got := stmt.ColumnText(0)
-		if got != "\xfe" {
-			t.Errorf("got %q", got)
-		}
-	}
-
-	if stmt.Step() {
-		got := stmt.ColumnText(0)
-		if got != "\xbe" {
-			t.Errorf("got %q", got)
-		}
-	}
-
-	err = stmt.Err()
+	err = stmt.Exec()
 	if err != nil {
-		t.Fatal(err)
+		t.Log(err)
 	}
 }
 
@@ -129,9 +224,6 @@ func Test_openblob(t *testing.T) {
 	}
 	defer db.Close()
 
-	blobio.Register(db)
-	array.Register(db)
-
 	err = db.Exec(`SELECT openblob()`)
 	if err == nil {
 		t.Fatal("want error")
@@ -139,6 +231,13 @@ func Test_openblob(t *testing.T) {
 		t.Log(err)
 	}
 
+	err = db.Exec(`SELECT openblob('main', 'test1', 'col', 1, false, NULL)`)
+	if err == nil {
+		t.Fatal("want error")
+	} else {
+		t.Log(err)
+	}
+
 	err = db.Exec(`
 		CREATE TABLE test1 (col);
 		CREATE TABLE test2 (col);
@@ -179,7 +278,7 @@ func Test_openblob(t *testing.T) {
 	}
 
 	want := []string{"\xca\xfe", "\xba\xbe"}
-	if !reflect.DeepEqual(got, want) {
+	if !slices.Equal(got, want) {
 		t.Errorf("got %v, want %v", got, want)
 	}
 }

ext/bloom/bloom.go

@@ -7,21 +7,22 @@
 package bloom
 
 import (
-	"errors"
 	"fmt"
 	"io"
 	"math"
 	"strconv"
 
 	"github.com/dchest/siphash"
+
 	"github.com/ncruces/go-sqlite3"
+	"github.com/ncruces/go-sqlite3/internal/util"
 )
 
 // Register registers the bloom_filter virtual table:
 //
 //	CREATE VIRTUAL TABLE foo USING bloom_filter(nElements, falseProb, kHashes)
-func Register(db *sqlite3.Conn) {
-	sqlite3.CreateModule(db, "bloom_filter", create, connect)
+func Register(db *sqlite3.Conn) error {
+	return sqlite3.CreateModule(db, "bloom_filter", create, connect)
 }
 
 type bloom struct {
@@ -34,7 +35,7 @@ type bloom struct {
 }
 
 func create(db *sqlite3.Conn, _, schema, table string, arg ...string) (_ *bloom, err error) {
-	t := bloom{
+	b := bloom{
 		db:      db,
 		schema:  schema,
 		storage: table + "_storage",
@@ -47,41 +48,47 @@ func create(db *sqlite3.Conn, _, schema, table string, arg ...string) (_ *bloom,
 			return nil, err
 		}
 		if nelem <= 0 {
-			return nil, errors.New("bloom: number of elements in filter must be positive")
+			return nil, util.ErrorString("bloom: number of elements in filter must be positive")
 		}
 	} else {
 		nelem = 100
 	}
 
 	if len(arg) > 1 {
-		t.prob, err = strconv.ParseFloat(arg[1], 64)
+		b.prob, err = strconv.ParseFloat(arg[1], 64)
 		if err != nil {
 			return nil, err
 		}
-		if t.prob <= 0 || t.prob >= 1 {
-			return nil, errors.New("bloom: probability must be in the range (0,1)")
+		if b.prob <= 0 || b.prob >= 1 {
+			return nil, util.ErrorString("bloom: probability must be in the range (0,1)")
 		}
 	} else {
-		t.prob = 0.01
+		b.prob = 0.01
 	}
 
 	if len(arg) > 2 {
-		t.hashes, err = strconv.Atoi(arg[2])
+		b.hashes, err = strconv.Atoi(arg[2])
 		if err != nil {
 			return nil, err
 		}
-		if t.hashes <= 0 {
-			return nil, errors.New("bloom: number of hash functions must be positive")
+		if b.hashes <= 0 {
+			return nil, util.ErrorString("bloom: number of hash functions must be positive")
 		}
 	} else {
-		t.hashes = max(1, numHashes(t.prob))
+		b.hashes = max(1, numHashes(b.prob))
 	}
 
-	t.bytes = numBytes(nelem, t.prob)
+	b.bytes = numBytes(nelem, b.prob)
+
+	err = db.DeclareVTab(
+		`CREATE TABLE x(present, word HIDDEN NOT NULL PRIMARY KEY) WITHOUT ROWID`)
+	if err != nil {
+		return nil, err
+	}
 
 	err = db.Exec(fmt.Sprintf(
 		`CREATE TABLE %s.%s (data BLOB, p REAL, n INTEGER, m INTEGER, k INTEGER)`,
-		sqlite3.QuoteIdentifier(t.schema), sqlite3.QuoteIdentifier(t.storage)))
+		sqlite3.QuoteIdentifier(b.schema), sqlite3.QuoteIdentifier(b.storage)))
 	if err != nil {
 		return nil, err
 	}
@@ -92,23 +99,17 @@ func create(db *sqlite3.Conn, _, schema, table string, arg ...string) (_ *bloom,
 	err = db.Exec(fmt.Sprintf(
 		`INSERT INTO %s.%s (rowid, data, p, n, m, k)
 		 VALUES (1, zeroblob(%d), %f, %d, %d, %d)`,
-		sqlite3.QuoteIdentifier(t.schema), sqlite3.QuoteIdentifier(t.storage),
-		t.bytes, t.prob, nelem, 8*t.bytes, t.hashes))
+		sqlite3.QuoteIdentifier(b.schema), sqlite3.QuoteIdentifier(b.storage),
+		b.bytes, b.prob, nelem, 8*b.bytes, b.hashes))
 	if err != nil {
+		b.Destroy()
 		return nil, err
 	}
-
-	err = db.DeclareVTab(
-		`CREATE TABLE x(present, word HIDDEN NOT NULL PRIMARY KEY) WITHOUT ROWID`)
-	if err != nil {
-		t.Destroy()
-		return nil, err
-	}
-	return &t, nil
+	return &b, nil
 }
 
 func connect(db *sqlite3.Conn, _, schema, table string, arg ...string) (_ *bloom, err error) {
-	t := bloom{
+	b := bloom{
 		db:      db,
 		schema:  schema,
 		storage: table + "_storage",
@@ -122,23 +123,23 @@ func connect(db *sqlite3.Conn, _, schema, table string, arg ...string) (_ *bloom
 
 	load, _, err := db.Prepare(fmt.Sprintf(
 		`SELECT m/8, p, k FROM %s.%s WHERE rowid = 1`,
-		sqlite3.QuoteIdentifier(t.schema), sqlite3.QuoteIdentifier(t.storage)))
+		sqlite3.QuoteIdentifier(b.schema), sqlite3.QuoteIdentifier(b.storage)))
 	if err != nil {
 		return nil, err
 	}
 	defer load.Close()
 
 	if !load.Step() {
-		if err = load.Err(); err == nil {
-			err = sqlite3.CORRUPT_VTAB
+		if err := load.Err(); err != nil {
+			return nil, err
 		}
-		return nil, err
+		return nil, sqlite3.CORRUPT_VTAB
 	}
 
-	t.bytes = load.ColumnInt64(0)
-	t.prob = load.ColumnFloat(1)
-	t.hashes = load.ColumnInt(2)
-	return &t, nil
+	b.bytes = load.ColumnInt64(0)
+	b.prob = load.ColumnFloat(1)
+	b.hashes = load.ColumnInt(2)
+	return &b, nil
 }
 
 func (b *bloom) Destroy() error {
@@ -160,7 +161,9 @@ func (b *bloom) Rename(new string) error {
 	return err
 }
 
-func (t *bloom) ShadowTables() {}
+func (t *bloom) ShadowTables() {
+	// notest // not meant to be called
+}
 
 func (t *bloom) Integrity(schema, table string, flags int) error {
 	load, _, err := t.db.Prepare(fmt.Sprintf(
@@ -171,7 +174,7 @@ func (t *bloom) Integrity(schema, table string, flags int) error {
 	}
 	defer load.Close()
 
-	err = errors.New("bloom: invalid parameters")
+	err = util.ErrorString("bloom: invalid parameters")
 	if !load.Step() {
 		return err
 	}
@@ -196,10 +199,10 @@ func (t *bloom) Integrity(schema, table string, flags int) error {
 }
 
 func (b *bloom) BestIndex(idx *sqlite3.IndexInfo) error {
-	for n, cst := range idx.Constraint {
+	for i, cst := range idx.Constraint {
 		if cst.Usable && cst.Column == 1 &&
 			cst.Op == sqlite3.INDEX_CONSTRAINT_EQ {
-			idx.ConstraintUsage[n].ArgvIndex = 1
+			idx.ConstraintUsage[i].ArgvIndex = 1
 			idx.OrderByConsumed = true
 			idx.EstimatedRows = 1
 			idx.EstimatedCost = float64(b.hashes)
@@ -213,11 +216,14 @@ func (b *bloom) BestIndex(idx *sqlite3.IndexInfo) error {
 func (b *bloom) Update(arg ...sqlite3.Value) (rowid int64, err error) {
 	if arg[0].Type() != sqlite3.NULL {
 		if len(arg) == 1 {
-			return 0, errors.New("bloom: elements cannot be deleted")
+			return 0, util.ErrorString("bloom: elements cannot be deleted")
 		}
-		return 0, errors.New("bloom: elements cannot be updated")
+		return 0, util.ErrorString("bloom: elements cannot be updated")
 	}
 
+	if arg[2].NoChange() {
+		return 0, nil
+	}
 	blob := arg[2].RawBlob()
 
 	f, err := b.db.OpenBlob(b.schema, b.storage, "data", 1, true)
@@ -226,7 +232,7 @@ func (b *bloom) Update(arg ...sqlite3.Value) (rowid int64, err error) {
 	}
 	defer f.Close()
 
-	for n := 0; n < b.hashes; n++ {
+	for n := range b.hashes {
 		hash := calcHash(n, blob)
 		hash %= uint64(b.bytes * 8)
 		bitpos := byte(hash % 8)
@@ -262,15 +268,11 @@ func (b *bloom) Open() (sqlite3.VTabCursor, error) {
 
 type cursor struct {
 	*bloom
-	eof bool
 	arg *sqlite3.Value
+	eof bool
 }
 
 func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
-	if len(arg) != 1 {
-		return nil
-	}
-
 	c.eof = false
 	c.arg = &arg[0]
 	blob := arg[0].RawBlob()
@@ -302,7 +304,10 @@ func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
 	return nil
 }
 
-func (c *cursor) Column(ctx *sqlite3.Context, n int) error {
+func (c *cursor) Column(ctx sqlite3.Context, n int) error {
+	if ctx.VTabNoChange() {
+		return nil
+	}
 	switch n {
 	case 0:
 		ctx.ResultBool(true)
@@ -322,6 +327,7 @@ func (c *cursor) EOF() bool {
 }
 
 func (c *cursor) RowID() (int64, error) {
+	// notest // WITHOUT ROWID
 	return 0, nil
 }
 

ext/bloom/bloom_test.go

@@ -12,6 +12,11 @@ import (
 	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
 )
 
+func TestMain(m *testing.M) {
+	sqlite3.AutoExtension(bloom.Register)
+	m.Run()
+}
+
 func TestRegister(t *testing.T) {
 	t.Parallel()
 
@@ -21,10 +26,8 @@ func TestRegister(t *testing.T) {
 	}
 	defer db.Close()
 
-	bloom.Register(db)
-
 	err = db.Exec(`
-		CREATE VIRTUAL TABLE sports_cars USING bloom_filter(20);
+		CREATE VIRTUAL TABLE sports_cars USING bloom_filter();
 		INSERT INTO sports_cars VALUES ('ferrari'), ('lamborghini'), ('alfa romeo')
 	`)
 	if err != nil {
@@ -66,7 +69,22 @@ func TestRegister(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.Exec(`DROP TABLE sports_cars`)
+	err = db.Exec(`DELETE FROM sports_cars WHERE word = 'lamborghini'`)
+	if err == nil {
+		t.Error("want error")
+	}
+
+	err = db.Exec(`UPDATE sports_cars SET word = 'ferrari' WHERE word = 'lamborghini'`)
+	if err == nil {
+		t.Error("want error")
+	}
+
+	err = db.Exec(`ALTER TABLE sports_cars RENAME TO fast_cars`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = db.Exec(`DROP TABLE fast_cars`)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -90,8 +108,6 @@ func Test_compatible(t *testing.T) {
 	}
 	defer db.Close()
 
-	bloom.Register(db)
-
 	query, _, err := db.Prepare(`SELECT COUNT(*) FROM plants(?)`)
 	if err != nil {
 		t.Fatal(err)
@@ -138,3 +154,42 @@ func Test_compatible(t *testing.T) {
 		t.Error(err)
 	}
 }
+
+func Test_errors(t *testing.T) {
+	t.Parallel()
+
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	bloom.Register(db)
+
+	err = db.Exec(`CREATE VIRTUAL TABLE sports_cars USING bloom_filter(0)`)
+	if err == nil {
+		t.Error("want error")
+	}
+	err = db.Exec(`CREATE VIRTUAL TABLE sports_cars USING bloom_filter('a')`)
+	if err == nil {
+		t.Error("want error")
+	}
+
+	err = db.Exec(`CREATE VIRTUAL TABLE sports_cars USING bloom_filter(20, 2)`)
+	if err == nil {
+		t.Error("want error")
+	}
+	err = db.Exec(`CREATE VIRTUAL TABLE sports_cars USING bloom_filter(20, 'a')`)
+	if err == nil {
+		t.Error("want error")
+	}
+
+	err = db.Exec(`CREATE VIRTUAL TABLE sports_cars USING bloom_filter(20, 0.9, 0)`)
+	if err == nil {
+		t.Error("want error")
+	}
+	err = db.Exec(`CREATE VIRTUAL TABLE sports_cars USING bloom_filter(20, 0.9, 'a')`)
+	if err == nil {
+		t.Error("want error")
+	}
+}

ext/closure/closure.go

@@ -0,0 +1,264 @@
+// Package closure provides a transitive closure virtual table.
+//
+// The transitive_closure virtual table finds the transitive closure of
+// a parent/child relationship in a real table.
+//
+// https://sqlite.org/src/doc/tip/ext/misc/closure.c
+package closure
+
+import (
+	"fmt"
+	"math"
+
+	"github.com/ncruces/go-sqlite3"
+	"github.com/ncruces/go-sqlite3/internal/util"
+	"github.com/ncruces/go-sqlite3/util/sql3util"
+)
+
+const (
+	_COL_ID           = 0
+	_COL_DEPTH        = 1
+	_COL_ROOT         = 2
+	_COL_TABLENAME    = 3
+	_COL_IDCOLUMN     = 4
+	_COL_PARENTCOLUMN = 5
+)
+
+// Register registers the transitive_closure virtual table:
+//
+//	CREATE VIRTUAL TABLE temp.closure USING transitive_closure;
+func Register(db *sqlite3.Conn) error {
+	return sqlite3.CreateModule(db, "transitive_closure", nil,
+		func(db *sqlite3.Conn, _, _, _ string, arg ...string) (*closure, error) {
+			var (
+				table  string
+				column string
+				parent string
+
+				done = util.Set[string]{}
+			)
+
+			for _, arg := range arg {
+				key, val := sql3util.NamedArg(arg)
+				if done.Contains(key) {
+					return nil, fmt.Errorf("transitive_closure: more than one %q parameter", key)
+				}
+				switch key {
+				case "tablename":
+					table = sql3util.Unquote(val)
+				case "idcolumn":
+					column = sql3util.Unquote(val)
+				case "parentcolumn":
+					parent = sql3util.Unquote(val)
+				default:
+					return nil, fmt.Errorf("transitive_closure: unknown %q parameter", key)
+				}
+				done.Add(key)
+			}
+
+			err := db.DeclareVTab(`CREATE TABLE x(id,depth,root HIDDEN,tablename HIDDEN,idcolumn HIDDEN,parentcolumn HIDDEN)`)
+			if err != nil {
+				return nil, err
+			}
+			return &closure{
+				db:     db,
+				table:  table,
+				column: column,
+				parent: parent,
+			}, nil
+		})
+}
+
+type closure struct {
+	db     *sqlite3.Conn
+	table  string
+	column string
+	parent string
+}
+
+func (c *closure) Destroy() error { return nil }
+
+func (c *closure) BestIndex(idx *sqlite3.IndexInfo) error {
+	plan := 0
+	posi := 1
+	cost := 1e7
+
+	for i, cst := range idx.Constraint {
+		switch {
+		case !cst.Usable:
+			continue
+
+		case plan&1 == 0 && cst.Column == _COL_ROOT:
+			switch cst.Op {
+			case sqlite3.INDEX_CONSTRAINT_EQ:
+				plan |= 1
+				cost /= 100
+				idx.ConstraintUsage[i] = sqlite3.IndexConstraintUsage{
+					ArgvIndex: 1,
+					Omit:      true,
+				}
+			}
+
+		case plan&0xf0 == 0 && cst.Column == _COL_DEPTH:
+			switch cst.Op {
+			case sqlite3.INDEX_CONSTRAINT_LT, sqlite3.INDEX_CONSTRAINT_LE, sqlite3.INDEX_CONSTRAINT_EQ:
+				plan |= posi << 4
+				cost /= 5
+				posi += 1
+				idx.ConstraintUsage[i].ArgvIndex = posi
+				if cst.Op == sqlite3.INDEX_CONSTRAINT_LT {
+					plan |= 2
+				}
+			}
+
+		case plan&0xf00 == 0 && cst.Column == _COL_TABLENAME:
+			switch cst.Op {
+			case sqlite3.INDEX_CONSTRAINT_EQ:
+				plan |= posi << 8
+				cost /= 5
+				posi += 1
+				idx.ConstraintUsage[i] = sqlite3.IndexConstraintUsage{
+					ArgvIndex: posi,
+					Omit:      true,
+				}
+			}
+
+		case plan&0xf000 == 0 && cst.Column == _COL_IDCOLUMN:
+			switch cst.Op {
+			case sqlite3.INDEX_CONSTRAINT_EQ:
+				plan |= posi << 12
+				posi += 1
+				idx.ConstraintUsage[i] = sqlite3.IndexConstraintUsage{
+					ArgvIndex: posi,
+					Omit:      true,
+				}
+			}
+
+		case plan&0xf0000 == 0 && cst.Column == _COL_PARENTCOLUMN:
+			switch cst.Op {
+			case sqlite3.INDEX_CONSTRAINT_EQ:
+				plan |= posi << 16
+				posi += 1
+				idx.ConstraintUsage[i] = sqlite3.IndexConstraintUsage{
+					ArgvIndex: posi,
+					Omit:      true,
+				}
+			}
+		}
+	}
+
+	if plan&1 == 0 ||
+		c.table == "" && plan&0xf00 == 0 ||
+		c.column == "" && plan&0xf000 == 0 ||
+		c.parent == "" && plan&0xf0000 == 0 {
+		return sqlite3.CONSTRAINT
+	}
+
+	idx.EstimatedCost = cost
+	idx.IdxNum = plan
+	return nil
+}
+
+func (c *closure) Open() (sqlite3.VTabCursor, error) {
+	return &cursor{closure: c}, nil
+}
+
+type cursor struct {
+	*closure
+	nodes []node
+}
+
+type node struct {
+	id    int64
+	depth int
+}
+
+func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
+	root := arg[0].Int64()
+	maxDepth := math.MaxInt
+	if idxNum&0xf0 != 0 {
+		maxDepth = arg[(idxNum>>4)&0xf].Int()
+		if idxNum&2 != 0 {
+			maxDepth -= 1
+		}
+	}
+	table := c.table
+	if idxNum&0xf00 != 0 {
+		table = arg[(idxNum>>8)&0xf].Text()
+	}
+	column := c.column
+	if idxNum&0xf000 != 0 {
+		column = arg[(idxNum>>12)&0xf].Text()
+	}
+	parent := c.parent
+	if idxNum&0xf0000 != 0 {
+		parent = arg[(idxNum>>16)&0xf].Text()
+	}
+
+	sql := fmt.Sprintf(
+		`SELECT %[1]s.%[2]s FROM %[1]s WHERE %[1]s.%[3]s=?`,
+		sqlite3.QuoteIdentifier(table),
+		sqlite3.QuoteIdentifier(column),
+		sqlite3.QuoteIdentifier(parent),
+	)
+	stmt, _, err := c.db.Prepare(sql)
+	if err != nil {
+		return err
+	}
+	defer stmt.Close()
+
+	c.nodes = []node{{root, 0}}
+	set := util.Set[int64]{}
+	set.Add(root)
+	for i := range c.nodes {
+		curr := c.nodes[i]
+		if curr.depth >= maxDepth {
+			continue
+		}
+		if err := stmt.BindInt64(1, curr.id); err != nil {
+			return err
+		}
+		for stmt.Step() {
+			if stmt.ColumnType(0) == sqlite3.INTEGER {
+				next := stmt.ColumnInt64(0)
+				if !set.Contains(next) {
+					set.Add(next)
+					c.nodes = append(c.nodes, node{next, curr.depth + 1})
+				}
+			}
+		}
+		if err := stmt.Reset(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (c *cursor) Column(ctx sqlite3.Context, n int) error {
+	switch n {
+	case _COL_ID:
+		ctx.ResultInt64(c.nodes[0].id)
+	case _COL_DEPTH:
+		ctx.ResultInt(c.nodes[0].depth)
+	case _COL_TABLENAME:
+		ctx.ResultText(c.table)
+	case _COL_IDCOLUMN:
+		ctx.ResultText(c.column)
+	case _COL_PARENTCOLUMN:
+		ctx.ResultText(c.parent)
+	}
+	return nil
+}
+
+func (c *cursor) Next() error {
+	c.nodes = c.nodes[1:]
+	return nil
+}
+
+func (c *cursor) EOF() bool {
+	return len(c.nodes) == 0
+}
+
+func (c *cursor) RowID() (int64, error) {
+	return c.nodes[0].id, nil
+}

ext/closure/closure_test.go

@@ -0,0 +1,184 @@
+package closure_test
+
+import (
+	_ "embed"
+	"fmt"
+	"log"
+	"testing"
+
+	"github.com/ncruces/go-sqlite3"
+	_ "github.com/ncruces/go-sqlite3/embed"
+	"github.com/ncruces/go-sqlite3/ext/closure"
+	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
+)
+
+func TestMain(m *testing.M) {
+	sqlite3.AutoExtension(closure.Register)
+	m.Run()
+}
+
+func Example() {
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer db.Close()
+
+	closure.Register(db)
+
+	err = db.Exec(`
+		CREATE TABLE employees (
+			id INTEGER PRIMARY KEY,
+			parent_id INTEGER,
+			name TEXT
+		);
+		CREATE INDEX employees_parent_idx ON employees(parent_id);
+		INSERT INTO employees (id, parent_id, name) VALUES
+			(11, NULL, 'Diane'),
+			(12, 11, 'Bob'),
+			(21, 11, 'Emma'),
+			(22, 21, 'Grace'),
+			(23, 21, 'Henry'),
+			(24, 21, 'Irene'),
+			(25, 21, 'Frank'),
+			(31, 11, 'Cindy'),
+			(32, 31, 'Dave'),
+			(33, 31, 'Alice');
+		CREATE VIRTUAL TABLE hierarchy USING transitive_closure(
+			tablename = "employees",
+			idcolumn = "id",
+			parentcolumn = "parent_id"
+		);
+	`)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	stmt, _, err := db.Prepare(`
+		SELECT employees.id, name FROM employees, hierarchy
+		WHERE employees.id = hierarchy.id AND hierarchy.root = 31
+	`)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer stmt.Close()
+
+	for stmt.Step() {
+		fmt.Println(stmt.ColumnInt(0), stmt.ColumnText(1))
+	}
+	if err := stmt.Err(); err != nil {
+		log.Fatal(err)
+	}
+
+	err = stmt.Close()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	err = db.Close()
+	if err != nil {
+		log.Fatal(err)
+	}
+	// Output:
+	// 31 Cindy
+	// 32 Dave
+	// 33 Alice
+}
+
+func TestRegister(t *testing.T) {
+	t.Parallel()
+
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	err = db.Exec(`
+		CREATE TABLE employees (
+			id INTEGER PRIMARY KEY,
+			parent_id INTEGER,
+			name TEXT
+		);
+		CREATE INDEX employees_parent_idx ON employees(parent_id);
+		INSERT INTO employees (id, parent_id, name) VALUES
+			(11, NULL, 'Diane'),
+			(12, 11, 'Bob'),
+			(21, 11, 'Emma'),
+			(22, 21, 'Grace'),
+			(23, 21, 'Henry'),
+			(24, 21, 'Irene'),
+			(25, 21, 'Frank'),
+			(31, 11, 'Cindy'),
+			(32, 31, 'Dave'),
+			(33, 31, 'Alice');
+		CREATE VIRTUAL TABLE temp.closure USING transitive_closure;
+	`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	stmt, _, err := db.Prepare(`
+		SELECT employees.id, name FROM employees, closure
+		 WHERE employees.id = closure.id
+		   AND closure.root = 31
+		   AND closure.depth < 1
+		   AND closure.tablename='employees'
+		   AND closure.idcolumn='id'
+		   AND closure.parentcolumn='parent_id'
+	`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer stmt.Close()
+
+	if !stmt.Step() {
+		t.Error("want row")
+	}
+	if stmt.Step() {
+		t.Error("don't want row")
+	}
+	if err := stmt.Err(); err != nil {
+		t.Fatal(err)
+	}
+
+	err = stmt.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = db.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func Test_errors(t *testing.T) {
+	t.Parallel()
+
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	err = db.Exec(`CREATE VIRTUAL TABLE hierarchy USING transitive_closure(table='employees')`)
+	if err == nil {
+		t.Error("want error")
+	}
+
+	err = db.Exec(`CREATE VIRTUAL TABLE hierarchy USING transitive_closure(tablename='employees', tablename="employees")`)
+	if err == nil {
+		t.Error("want error")
+	}
+
+	err = db.Exec("CREATE VIRTUAL TABLE hierarchy USING transitive_closure(tablename=`employees`)")
+	if err != nil {
+		t.Error(err)
+	}
+
+	err = db.Exec(`SELECT * FROM hierarchy`)
+	if err == nil {
+		t.Error("want error")
+	}
+}

ext/csv/arg.go

@@ -4,8 +4,7 @@ import (
 	"fmt"
 	"strconv"
 
-	"github.com/ncruces/go-sqlite3/internal/util"
-	"github.com/ncruces/go-sqlite3/util/vtabutil"
+	"github.com/ncruces/go-sqlite3/util/sql3util"
 )
 
 func uintArg(key, val string) (int, error) {
@@ -20,7 +19,7 @@ func boolArg(key, val string) (bool, error) {
 	if val == "" {
 		return true, nil
 	}
-	b, ok := util.ParseBool(val)
+	b, ok := sql3util.ParseBool(val)
 	if ok {
 		return b, nil
 	}
@@ -28,7 +27,7 @@ func boolArg(key, val string) (bool, error) {
 }
 
 func runeArg(key, val string) (rune, error) {
-	r, _, tail, err := strconv.UnquoteChar(vtabutil.Unquote(val), 0)
+	r, _, tail, err := strconv.UnquoteChar(sql3util.Unquote(val), 0)
 	if tail != "" || err != nil {
 		return 0, fmt.Errorf("csv: invalid %q parameter: %s", key, val)
 	}

ext/csv/arg_test.go

@@ -3,7 +3,7 @@ package csv
 import (
 	"testing"
 
-	"github.com/ncruces/go-sqlite3/util/vtabutil"
+	"github.com/ncruces/go-sqlite3/util/sql3util"
 )
 
 func Test_uintArg(t *testing.T) {
@@ -24,7 +24,7 @@ func Test_uintArg(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.arg, func(t *testing.T) {
-			key, val := vtabutil.NamedArg(tt.arg)
+			key, val := sql3util.NamedArg(tt.arg)
 			if key != tt.key {
 				t.Errorf("NamedArg() %v, want err %v", key, tt.key)
 			}
@@ -62,7 +62,7 @@ func Test_boolArg(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.arg, func(t *testing.T) {
-			key, val := vtabutil.NamedArg(tt.arg)
+			key, val := sql3util.NamedArg(tt.arg)
 			if key != tt.key {
 				t.Errorf("NamedArg() %v, want err %v", key, tt.key)
 			}
@@ -96,7 +96,7 @@ func Test_runeArg(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.arg, func(t *testing.T) {
-			key, val := vtabutil.NamedArg(tt.arg)
+			key, val := sql3util.NamedArg(tt.arg)
 			if key != tt.key {
 				t.Errorf("NamedArg() %v, want err %v", key, tt.key)
 			}

ext/csv/csv.go

@@ -9,7 +9,6 @@ package csv
 import (
 	"bufio"
 	"encoding/csv"
-	"errors"
 	"fmt"
 	"io"
 	"io/fs"
@@ -17,19 +16,20 @@ import (
 	"strings"
 
 	"github.com/ncruces/go-sqlite3"
+	"github.com/ncruces/go-sqlite3/internal/util"
 	"github.com/ncruces/go-sqlite3/util/osutil"
-	"github.com/ncruces/go-sqlite3/util/vtabutil"
+	"github.com/ncruces/go-sqlite3/util/sql3util"
 )
 
 // Register registers the CSV virtual table.
 // If a filename is specified, [os.Open] is used to open the file.
-func Register(db *sqlite3.Conn) {
-	RegisterFS(db, osutil.FS{})
+func Register(db *sqlite3.Conn) error {
+	return RegisterFS(db, osutil.FS{})
 }
 
 // RegisterFS registers the CSV virtual table.
 // If a filename is specified, fsys is used to open the file.
-func RegisterFS(db *sqlite3.Conn, fsys fs.FS) {
+func RegisterFS(db *sqlite3.Conn, fsys fs.FS) error {
 	declare := func(db *sqlite3.Conn, _, _, _ string, arg ...string) (_ *table, err error) {
 		var (
 			filename string
@@ -40,21 +40,21 @@ func RegisterFS(db *sqlite3.Conn, fsys fs.FS) {
 			comma    rune = ','
 			comment  rune
 
-			done = map[string]struct{}{}
+			done = util.Set[string]{}
 		)
 
 		for _, arg := range arg {
-			key, val := vtabutil.NamedArg(arg)
-			if _, ok := done[key]; ok {
+			key, val := sql3util.NamedArg(arg)
+			if done.Contains(key) {
 				return nil, fmt.Errorf("csv: more than one %q parameter", key)
 			}
 			switch key {
 			case "filename":
-				filename = vtabutil.Unquote(val)
+				filename = sql3util.Unquote(val)
 			case "data":
-				data = vtabutil.Unquote(val)
+				data = sql3util.Unquote(val)
 			case "schema":
-				schema = vtabutil.Unquote(val)
+				schema = sql3util.Unquote(val)
 			case "header":
 				header, err = boolArg(key, val)
 			case "columns":
@@ -69,14 +69,14 @@ func RegisterFS(db *sqlite3.Conn, fsys fs.FS) {
 			if err != nil {
 				return nil, err
 			}
-			done[key] = struct{}{}
+			done.Add(key)
 		}
 
 		if (filename == "") == (data == "") {
-			return nil, errors.New(`csv: must specify either "filename" or "data" but not both`)
+			return nil, util.ErrorString(`csv: must specify either "filename" or "data" but not both`)
 		}
 
-		table := &table{
+		t := &table{
 			fsys:    fsys,
 			name:    filename,
 			data:    data,
@@ -88,7 +88,7 @@ func RegisterFS(db *sqlite3.Conn, fsys fs.FS) {
 		if schema == "" {
 			var row []string
 			if header || columns < 0 {
-				csv, c, err := table.newReader()
+				csv, c, err := t.newReader()
 				defer c.Close()
 				if err != nil {
 					return nil, err
@@ -100,25 +100,23 @@ func RegisterFS(db *sqlite3.Conn, fsys fs.FS) {
 			}
 			schema = getSchema(header, columns, row)
 		} else {
-			defer func() {
-				if err == nil {
-					table.typs, err = getColumnAffinities(schema)
-				}
-			}()
+			t.typs, err = getColumnAffinities(schema)
+			if err != nil {
+				return nil, err
+			}
 		}
 
 		err = db.DeclareVTab(schema)
+		if err == nil {
+			err = db.VTabConfig(sqlite3.VTAB_DIRECTONLY)
+		}
 		if err != nil {
 			return nil, err
 		}
-		err = db.VTabConfig(sqlite3.VTAB_DIRECTONLY)
-		if err != nil {
-			return nil, err
-		}
-		return table, nil
+		return t, nil
 	}
 
-	sqlite3.CreateModule(db, "csv", declare, declare)
+	return sqlite3.CreateModule(db, "csv", declare, declare)
 }
 
 type table struct {
@@ -216,7 +214,10 @@ func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
 		return err
 	}
 	if c.table.header {
-		c.Next() // skip header
+		err = c.Next() // skip header
+		if err != nil {
+			return err
+		}
 	}
 	c.rowID = 0
 	return c.Next()
@@ -239,7 +240,7 @@ func (c *cursor) RowID() (int64, error) {
 	return c.rowID, nil
 }
 
-func (c *cursor) Column(ctx *sqlite3.Context, col int) error {
+func (c *cursor) Column(ctx sqlite3.Context, col int) error {
 	if col < len(c.row) {
 		typ := text
 		if col < len(c.table.typs) {

ext/csv/csv_test.go

@@ -18,7 +18,10 @@ func Example() {
 	}
 	defer db.Close()
 
-	csv.Register(db)
+	err = csv.Register(db)
+	if err != nil {
+		log.Fatal(err)
+	}
 
 	err = db.Exec(`
 		CREATE VIRTUAL TABLE eurofxref USING csv(
@@ -51,6 +54,11 @@ func Example() {
 	// On Twosday, 1€ = $1.1342
 }
 
+func TestMain(m *testing.M) {
+	sqlite3.AutoExtension(csv.Register)
+	m.Run()
+}
+
 func TestRegister(t *testing.T) {
 	t.Parallel()
 
@@ -60,8 +68,6 @@ func TestRegister(t *testing.T) {
 	}
 	defer db.Close()
 
-	csv.Register(db)
-
 	const data = `
 # Comment
 "Rob"	"Pike"	rob
@@ -124,8 +130,6 @@ func TestAffinity(t *testing.T) {
 	}
 	defer db.Close()
 
-	csv.Register(db)
-
 	const data = "01\n0.10\ne"
 	err = db.Exec(`
 		CREATE VIRTUAL TABLE temp.nums USING csv(
@@ -168,8 +172,6 @@ func TestRegister_errors(t *testing.T) {
 	}
 	defer db.Close()
 
-	csv.Register(db)
-
 	err = db.Exec(`CREATE VIRTUAL TABLE temp.users USING csv()`)
 	if err == nil {
 		t.Fatal("want error")

ext/csv/types.go

@@ -1,10 +1,9 @@
 package csv
 
 import (
-	_ "embed"
 	"strings"
 
-	"github.com/ncruces/go-sqlite3/util/vtabutil"
+	"github.com/ncruces/go-sqlite3/util/sql3util"
 )
 
 type affinity byte
@@ -18,16 +17,15 @@ const (
 )
 
 func getColumnAffinities(schema string) ([]affinity, error) {
-	tab, err := vtabutil.Parse(schema)
+	tab, err := sql3util.ParseTable(schema)
 	if err != nil {
 		return nil, err
 	}
-	defer tab.Close()
 
-	types := make([]affinity, tab.NumColumns())
-	for i := range types {
-		col := tab.Column(i)
-		types[i] = getAffinity(col.Type())
+	columns := tab.Columns
+	types := make([]affinity, len(columns))
+	for i, col := range columns {
+		types[i] = getAffinity(col.Type)
 	}
 	return types, nil
 }

ext/csv/types_test.go

@@ -1,9 +1,6 @@
 package csv
 
-import (
-	_ "embed"
-	"testing"
-)
+import "testing"
 
 func Test_getAffinity(t *testing.T) {
 	tests := []struct {

ext/fileio/coro.go

@@ -1,3 +1,5 @@
+//go:build !go1.23
+
 package fileio
 
 import (

ext/fileio/fileio.go

@@ -14,24 +14,28 @@ import (
 
 // Register registers SQL functions readfile, writefile, lsmode,
 // and the table-valued function fsdir.
-func Register(db *sqlite3.Conn) {
-	RegisterFS(db, nil)
+func Register(db *sqlite3.Conn) error {
+	return RegisterFS(db, nil)
 }
 
 // Register registers SQL functions readfile, lsmode,
 // and the table-valued function fsdir;
 // fsys will be used to read files and list directories.
-func RegisterFS(db *sqlite3.Conn, fsys fs.FS) {
-	db.CreateFunction("lsmode", 1, sqlite3.DETERMINISTIC, lsmode)
-	db.CreateFunction("readfile", 1, sqlite3.DIRECTONLY, readfile(fsys))
+func RegisterFS(db *sqlite3.Conn, fsys fs.FS) error {
+	var err error
 	if fsys == nil {
-		db.CreateFunction("writefile", -1, sqlite3.DIRECTONLY, writefile)
+		err = db.CreateFunction("writefile", -1, sqlite3.DIRECTONLY, writefile)
 	}
-	sqlite3.CreateModule(db, "fsdir", nil, func(db *sqlite3.Conn, _, _, _ string, _ ...string) (fsdir, error) {
-		err := db.DeclareVTab(`CREATE TABLE x(name,mode,mtime TIMESTAMP,data,path HIDDEN,dir HIDDEN)`)
-		db.VTabConfig(sqlite3.VTAB_DIRECTONLY)
-		return fsdir{fsys}, err
-	})
+	return errors.Join(err,
+		db.CreateFunction("readfile", 1, sqlite3.DIRECTONLY, readfile(fsys)),
+		db.CreateFunction("lsmode", 1, sqlite3.DETERMINISTIC, lsmode),
+		sqlite3.CreateModule(db, "fsdir", nil, func(db *sqlite3.Conn, _, _, _ string, _ ...string) (fsdir, error) {
+			err := db.DeclareVTab(`CREATE TABLE x(name,mode,mtime TIMESTAMP,data,path HIDDEN,dir HIDDEN)`)
+			if err == nil {
+				err = db.VTabConfig(sqlite3.VTAB_DIRECTONLY)
+			}
+			return fsdir{fsys}, err
+		}))
 }
 
 func lsmode(ctx sqlite3.Context, arg ...sqlite3.Value) {
@@ -53,7 +57,7 @@ func readfile(fsys fs.FS) func(ctx sqlite3.Context, arg ...sqlite3.Value) {
 		case err == nil:
 			ctx.ResultBlob(data)
 		case !errors.Is(err, fs.ErrNotExist):
-			ctx.ResultError(fmt.Errorf("readfile: %w", err))
+			ctx.ResultError(fmt.Errorf("readfile: %w", err)) // notest
 		}
 	}
 }

ext/fileio/fileio_test.go

@@ -12,15 +12,14 @@ import (
 	_ "github.com/ncruces/go-sqlite3/embed"
 	"github.com/ncruces/go-sqlite3/ext/fileio"
 	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
+	"github.com/ncruces/go-sqlite3/vfs/memdb"
 )
 
 func Test_lsmode(t *testing.T) {
 	t.Parallel()
+	tmp := memdb.TestDB(t)
 
-	db, err := driver.Open(":memory:", func(c *sqlite3.Conn) error {
-		fileio.Register(c)
-		return nil
-	})
+	db, err := driver.Open(tmp, fileio.Register)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -54,7 +53,9 @@ func Test_readfile(t *testing.T) {
 
 	for _, fsys := range []fs.FS{nil, os.DirFS(".")} {
 		t.Run("", func(t *testing.T) {
-			db, err := driver.Open(":memory:", func(c *sqlite3.Conn) error {
+			tmp := memdb.TestDB(t)
+
+			db, err := driver.Open(tmp, func(c *sqlite3.Conn) error {
 				fileio.RegisterFS(c, fsys)
 				return nil
 			})

ext/fileio/fsdir.go

@@ -10,13 +10,22 @@ import (
 	"github.com/ncruces/go-sqlite3"
 )
 
+const (
+	_COL_NAME = 0
+	_COL_MODE = 1
+	_COL_TIME = 2
+	_COL_DATA = 3
+	_COL_ROOT = 4
+	_COL_BASE = 5
+)
+
 type fsdir struct{ fsys fs.FS }
 
 func (d fsdir) BestIndex(idx *sqlite3.IndexInfo) error {
 	var root, base bool
 	for i, cst := range idx.Constraint {
 		switch cst.Column {
-		case 4: // root
+		case _COL_ROOT:
 			if !cst.Usable || cst.Op != sqlite3.INDEX_CONSTRAINT_EQ {
 				return sqlite3.CONSTRAINT
 			}
@@ -25,7 +34,7 @@ func (d fsdir) BestIndex(idx *sqlite3.IndexInfo) error {
 				ArgvIndex: 1,
 			}
 			root = true
-		case 5: // base
+		case _COL_BASE:
 			if !cst.Usable || cst.Op != sqlite3.INDEX_CONSTRAINT_EQ {
 				return sqlite3.CONSTRAINT
 			}
@@ -54,7 +63,7 @@ func (d fsdir) Open() (sqlite3.VTabCursor, error) {
 type cursor struct {
 	fsdir
 	base   string
-	resume func(struct{}) (entry, bool)
+	resume resume
 	cancel func()
 	curr   entry
 	eof    bool
@@ -92,25 +101,14 @@ func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
 		c.base = base
 	}
 
-	c.resume, c.cancel = coroNew(func(_ struct{}, yield func(entry) struct{}) entry {
-		walkDir := func(path string, d fs.DirEntry, err error) error {
-			yield(entry{d, err, path})
-			return nil
-		}
-		if c.fsys != nil {
-			fs.WalkDir(c.fsys, root, walkDir)
-		} else {
-			filepath.WalkDir(root, walkDir)
-		}
-		return entry{}
-	})
+	c.resume, c.cancel = pull(c, root)
 	c.eof = false
 	c.rowID = 0
 	return c.Next()
 }
 
 func (c *cursor) Next() error {
-	curr, ok := c.resume(struct{}{})
+	curr, ok := next(c)
 	c.curr = curr
 	c.eof = !ok
 	c.rowID++
@@ -125,27 +123,27 @@ func (c *cursor) RowID() (int64, error) {
 	return c.rowID, nil
 }
 
-func (c *cursor) Column(ctx *sqlite3.Context, n int) error {
+func (c *cursor) Column(ctx sqlite3.Context, n int) error {
 	switch n {
-	case 0: // name
+	case _COL_NAME:
 		name := strings.TrimPrefix(c.curr.path, c.base)
 		ctx.ResultText(name)
 
-	case 1: // mode
+	case _COL_MODE:
 		i, err := c.curr.Info()
 		if err != nil {
 			return err
 		}
 		ctx.ResultInt64(int64(i.Mode()))
 
-	case 2: // mtime
+	case _COL_TIME:
 		i, err := c.curr.Info()
 		if err != nil {
 			return err
 		}
 		ctx.ResultTime(i.ModTime(), sqlite3.TimeFormatUnixFrac)
 
-	case 3: // data
+	case _COL_DATA:
 		switch typ := c.curr.Type(); {
 		case typ.IsRegular():
 			var data []byte

ext/fileio/fsdir_coro.go

@@ -0,0 +1,29 @@
+//go:build !go1.23
+
+package fileio
+
+import (
+	"io/fs"
+	"path/filepath"
+)
+
+type resume = func(struct{}) (entry, bool)
+
+func next(c *cursor) (entry, bool) {
+	return c.resume(struct{}{})
+}
+
+func pull(c *cursor, root string) (resume, func()) {
+	return coroNew(func(_ struct{}, yield func(entry) struct{}) entry {
+		walkDir := func(path string, d fs.DirEntry, err error) error {
+			yield(entry{d, err, path})
+			return nil
+		}
+		if c.fsys != nil {
+			fs.WalkDir(c.fsys, root, walkDir)
+		} else {
+			filepath.WalkDir(root, walkDir)
+		}
+		return entry{}
+	})
+}

ext/fileio/fsdir_iter.go

@@ -0,0 +1,31 @@
+//go:build go1.23
+
+package fileio
+
+import (
+	"io/fs"
+	"iter"
+	"path/filepath"
+)
+
+type resume = func() (entry, bool)
+
+func next(c *cursor) (entry, bool) {
+	return c.resume()
+}
+
+func pull(c *cursor, root string) (resume, func()) {
+	return iter.Pull(func(yield func(entry) bool) {
+		walkDir := func(path string, d fs.DirEntry, err error) error {
+			if yield(entry{d, err, path}) {
+				return nil
+			}
+			return fs.SkipAll
+		}
+		if c.fsys != nil {
+			fs.WalkDir(c.fsys, root, walkDir)
+		} else {
+			filepath.WalkDir(root, walkDir)
+		}
+	})
+}

ext/fileio/fsdir_test.go

@@ -13,6 +13,7 @@ import (
 	_ "github.com/ncruces/go-sqlite3/embed"
 	"github.com/ncruces/go-sqlite3/ext/fileio"
 	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
+	"github.com/ncruces/go-sqlite3/vfs/memdb"
 )
 
 func Test_fsdir(t *testing.T) {
@@ -20,7 +21,9 @@ func Test_fsdir(t *testing.T) {
 
 	for _, fsys := range []fs.FS{nil, os.DirFS(".")} {
 		t.Run("", func(t *testing.T) {
-			db, err := driver.Open(":memory:", func(c *sqlite3.Conn) error {
+			tmp := memdb.TestDB(t)
+
+			db, err := driver.Open(tmp, func(c *sqlite3.Conn) error {
 				fileio.RegisterFS(c, fsys)
 				return nil
 			})
@@ -68,7 +71,10 @@ func Test_fsdir_errors(t *testing.T) {
 	}
 	defer db.Close()
 
-	fileio.Register(db)
+	err = fileio.Register(db)
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	err = db.Exec(`SELECT name FROM fsdir()`)
 	if err == nil {

ext/fileio/write.go

@@ -29,7 +29,7 @@ func writefile(ctx sqlite3.Context, arg ...sqlite3.Value) {
 	n, err := createFileAndDir(file, mode, arg[1])
 	if err != nil {
 		if len(arg) > 2 {
-			ctx.ResultError(fmt.Errorf("writefile: %w", err))
+			ctx.ResultError(fmt.Errorf("writefile: %w", err)) // notest
 		}
 		return
 	}
@@ -39,7 +39,7 @@ func writefile(ctx sqlite3.Context, arg ...sqlite3.Value) {
 			err := os.Chmod(file, mode.Perm())
 			if err != nil {
 				ctx.ResultError(fmt.Errorf("writefile: %w", err))
-				return
+				return // notest
 			}
 		}
 
@@ -48,7 +48,7 @@ func writefile(ctx sqlite3.Context, arg ...sqlite3.Value) {
 			err := os.Chtimes(file, time.Time{}, mtime)
 			if err != nil {
 				ctx.ResultError(fmt.Errorf("writefile: %w", err))
-				return
+				return // notest
 			}
 		}
 	}

ext/fileio/write_test.go

@@ -7,19 +7,17 @@ import (
 	"testing"
 	"time"
 
-	"github.com/ncruces/go-sqlite3"
 	"github.com/ncruces/go-sqlite3/driver"
 	_ "github.com/ncruces/go-sqlite3/embed"
 	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
+	"github.com/ncruces/go-sqlite3/vfs/memdb"
 )
 
 func Test_writefile(t *testing.T) {
 	t.Parallel()
+	tmp := memdb.TestDB(t)
 
-	db, err := driver.Open(":memory:", func(c *sqlite3.Conn) error {
-		Register(c)
-		return nil
-	})
+	db, err := driver.Open(tmp, Register)
 	if err != nil {
 		t.Fatal(err)
 	}

ext/hash/hash.go

@@ -21,47 +21,60 @@ package hash
 
 import (
 	"crypto"
+	"errors"
 
 	"github.com/ncruces/go-sqlite3"
+	"github.com/ncruces/go-sqlite3/internal/util"
 )
 
 // Register registers cryptographic hash functions for a database connection.
-func Register(db *sqlite3.Conn) {
-	flags := sqlite3.DETERMINISTIC | sqlite3.INNOCUOUS
+func Register(db *sqlite3.Conn) error {
+	const flags = sqlite3.DETERMINISTIC | sqlite3.INNOCUOUS
 
+	var errs util.ErrorJoiner
 	if crypto.MD4.Available() {
-		db.CreateFunction("md4", 1, flags, md4Func)
+		errs.Join(
+			db.CreateFunction("md4", 1, flags, md4Func))
 	}
 	if crypto.MD5.Available() {
-		db.CreateFunction("md5", 1, flags, md5Func)
+		errs.Join(
+			db.CreateFunction("md5", 1, flags, md5Func))
 	}
 	if crypto.SHA1.Available() {
-		db.CreateFunction("sha1", 1, flags, sha1Func)
+		errs.Join(
+			db.CreateFunction("sha1", 1, flags, sha1Func))
 	}
 	if crypto.SHA3_512.Available() {
-		db.CreateFunction("sha3", 1, flags, sha3Func)
-		db.CreateFunction("sha3", 2, flags, sha3Func)
+		errs.Join(
+			db.CreateFunction("sha3", 1, flags, sha3Func),
+			db.CreateFunction("sha3", 2, flags, sha3Func))
 	}
 	if crypto.SHA256.Available() {
-		db.CreateFunction("sha224", 1, flags, sha224Func)
-		db.CreateFunction("sha256", 1, flags, sha256Func)
-		db.CreateFunction("sha256", 2, flags, sha256Func)
+		errs.Join(
+			db.CreateFunction("sha224", 1, flags, sha224Func),
+			db.CreateFunction("sha256", 1, flags, sha256Func),
+			db.CreateFunction("sha256", 2, flags, sha256Func))
 	}
 	if crypto.SHA512.Available() {
-		db.CreateFunction("sha384", 1, flags, sha384Func)
-		db.CreateFunction("sha512", 1, flags, sha512Func)
-		db.CreateFunction("sha512", 2, flags, sha512Func)
+		errs.Join(
+			db.CreateFunction("sha384", 1, flags, sha384Func),
+			db.CreateFunction("sha512", 1, flags, sha512Func),
+			db.CreateFunction("sha512", 2, flags, sha512Func))
 	}
 	if crypto.BLAKE2s_256.Available() {
-		db.CreateFunction("blake2s", 1, flags, blake2sFunc)
+		errs.Join(
+			db.CreateFunction("blake2s", 1, flags, blake2sFunc))
 	}
 	if crypto.BLAKE2b_512.Available() {
-		db.CreateFunction("blake2b", 1, flags, blake2bFunc)
-		db.CreateFunction("blake2b", 2, flags, blake2bFunc)
+		errs.Join(
+			db.CreateFunction("blake2b", 1, flags, blake2bFunc),
+			db.CreateFunction("blake2b", 2, flags, blake2bFunc))
 	}
 	if crypto.RIPEMD160.Available() {
-		db.CreateFunction("ripemd160", 1, flags, ripemd160Func)
+		errs.Join(
+			db.CreateFunction("ripemd160", 1, flags, ripemd160Func))
 	}
+	return errors.Join(errs...)
 }
 
 func md4Func(ctx sqlite3.Context, arg ...sqlite3.Value) {

ext/hash/hash_test.go

@@ -7,19 +7,21 @@ import (
 	_ "crypto/sha512"
 	"testing"
 
-	"github.com/ncruces/go-sqlite3"
-	"github.com/ncruces/go-sqlite3/driver"
-	_ "github.com/ncruces/go-sqlite3/embed"
-	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
 	_ "golang.org/x/crypto/blake2b"
 	_ "golang.org/x/crypto/blake2s"
 	_ "golang.org/x/crypto/md4"
 	_ "golang.org/x/crypto/ripemd160"
 	_ "golang.org/x/crypto/sha3"
+
+	"github.com/ncruces/go-sqlite3/driver"
+	_ "github.com/ncruces/go-sqlite3/embed"
+	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
+	"github.com/ncruces/go-sqlite3/vfs/memdb"
 )
 
 func TestRegister(t *testing.T) {
 	t.Parallel()
+	tmp := memdb.TestDB(t)
 
 	tests := []struct {
 		name string
@@ -53,10 +55,7 @@ func TestRegister(t *testing.T) {
 		{"blake2b('', 256)", "0E5751C026E543B2E8AB2EB06099DAA1D1E5DF47778F7787FAAB45CDF12FE3A8"},
 	}
 
-	db, err := driver.Open(":memory:", func(c *sqlite3.Conn) error {
-		Register(c)
-		return nil
-	})
+	db, err := driver.Open(tmp, Register)
 	if err != nil {
 		t.Fatal(err)
 	}

ext/lines/lines.go

@@ -13,6 +13,7 @@ package lines
 import (
 	"bufio"
 	"bytes"
+	"errors"
 	"fmt"
 	"io"
 	"io/fs"
@@ -25,46 +26,61 @@ import (
 // The lines function reads from a database blob or text.
 // The lines_read function reads from a file or an [io.Reader].
 // If a filename is specified, [os.Open] is used to open the file.
-func Register(db *sqlite3.Conn) {
-	RegisterFS(db, osutil.FS{})
+func Register(db *sqlite3.Conn) error {
+	return RegisterFS(db, osutil.FS{})
 }
 
 // RegisterFS registers the lines and lines_read table-valued functions.
 // The lines function reads from a database blob or text.
 // The lines_read function reads from a file or an [io.Reader].
 // If a filename is specified, fsys is used to open the file.
-func RegisterFS(db *sqlite3.Conn, fsys fs.FS) {
-	sqlite3.CreateModule(db, "lines", nil,
-		func(db *sqlite3.Conn, _, _, _ string, _ ...string) (lines, error) {
-			err := db.DeclareVTab(`CREATE TABLE x(line TEXT, data HIDDEN)`)
-			db.VTabConfig(sqlite3.VTAB_INNOCUOUS)
-			return lines{}, err
-		})
-	sqlite3.CreateModule(db, "lines_read", nil,
-		func(db *sqlite3.Conn, _, _, _ string, _ ...string) (lines, error) {
-			err := db.DeclareVTab(`CREATE TABLE x(line TEXT, data HIDDEN)`)
-			db.VTabConfig(sqlite3.VTAB_DIRECTONLY)
-			return lines{fsys}, err
-		})
+func RegisterFS(db *sqlite3.Conn, fsys fs.FS) error {
+	return errors.Join(
+		sqlite3.CreateModule(db, "lines", nil,
+			func(db *sqlite3.Conn, _, _, _ string, _ ...string) (lines, error) {
+				err := db.DeclareVTab(`CREATE TABLE x(line TEXT, data HIDDEN, delim HIDDEN)`)
+				if err == nil {
+					err = db.VTabConfig(sqlite3.VTAB_INNOCUOUS)
+				}
+				return lines{}, err
+			}),
+		sqlite3.CreateModule(db, "lines_read", nil,
+			func(db *sqlite3.Conn, _, _, _ string, _ ...string) (lines, error) {
+				err := db.DeclareVTab(`CREATE TABLE x(line TEXT, data HIDDEN, delim HIDDEN)`)
+				if err == nil {
+					err = db.VTabConfig(sqlite3.VTAB_DIRECTONLY)
+				}
+				return lines{fsys}, err
+			}))
 }
 
 type lines struct {
 	fsys fs.FS
 }
 
-func (l lines) BestIndex(idx *sqlite3.IndexInfo) error {
+func (l lines) BestIndex(idx *sqlite3.IndexInfo) (err error) {
+	err = sqlite3.CONSTRAINT
 	for i, cst := range idx.Constraint {
-		if cst.Column == 1 && cst.Op == sqlite3.INDEX_CONSTRAINT_EQ && cst.Usable {
+		if !cst.Usable || cst.Op != sqlite3.INDEX_CONSTRAINT_EQ {
+			continue
+		}
+		switch cst.Column {
+		case 1:
 			idx.ConstraintUsage[i] = sqlite3.IndexConstraintUsage{
 				Omit:      true,
 				ArgvIndex: 1,
 			}
 			idx.EstimatedCost = 1e6
 			idx.EstimatedRows = 100
-			return nil
+			err = nil
+		case 2:
+			idx.ConstraintUsage[i] = sqlite3.IndexConstraintUsage{
+				Omit:      true,
+				ArgvIndex: 2,
+			}
 		}
 	}
-	return sqlite3.CONSTRAINT
+	return err
 }
 
 func (l lines) Open() (sqlite3.VTabCursor, error) {
@@ -79,6 +95,7 @@ type cursor struct {
 	line  []byte
 	rowID int64
 	eof   bool
+	delim byte
 }
 
 func (c *cursor) EOF() bool {
@@ -89,7 +106,7 @@ func (c *cursor) RowID() (int64, error) {
 	return c.rowID, nil
 }
 
-func (c *cursor) Column(ctx *sqlite3.Context, n int) error {
+func (c *cursor) Column(ctx sqlite3.Context, n int) error {
 	if n == 0 {
 		ctx.ResultRawText(c.line)
 	}
@@ -134,6 +151,15 @@ func (c *reader) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
 		return fmt.Errorf("lines: unsupported argument:%.0w %v", sqlite3.MISMATCH, typ)
 	}
 
+	c.delim = '\n'
+	if len(arg) > 1 {
+		b := arg[1].RawText()
+		if len(b) != 1 {
+			return fmt.Errorf("lines: delimiter must be a single byte%.0w", sqlite3.MISMATCH)
+		}
+		c.delim = b[0]
+	}
+
 	c.reader = bufio.NewReader(r)
 	c.closer, _ = r.(io.Closer)
 	c.rowID = 0
@@ -144,7 +170,12 @@ func (c *reader) Next() (err error) {
 	c.line = c.line[:0]
 	for more := true; more; {
 		var line []byte
-		line, more, err = c.reader.ReadLine()
+		if c.delim == '\n' {
+			line, more, err = c.reader.ReadLine()
+		} else {
+			line, err = c.reader.ReadSlice(c.delim)
+			more = err == bufio.ErrBufferFull
+		}
 		c.line = append(c.line, line...)
 	}
 	if err == io.EOF {
@@ -171,18 +202,27 @@ func (c *buffer) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
 		return fmt.Errorf("lines: unsupported argument:%.0w %v", sqlite3.MISMATCH, typ)
 	}
 
+	c.delim = '\n'
+	if len(arg) > 1 {
+		b := arg[1].RawText()
+		if len(b) != 1 {
+			return fmt.Errorf("lines: delimiter must be a single byte%.0w", sqlite3.MISMATCH)
+		}
+		c.delim = b[0]
+	}
+
 	c.rowID = 0
 	return c.Next()
 }
 
 func (c *buffer) Next() error {
-	i := bytes.IndexByte(c.data, '\n')
+	i := bytes.IndexByte(c.data, c.delim)
 	j := i + 1
 	switch {
 	case i < 0:
 		i = len(c.data)
 		j = i
-	case i > 0 && c.data[i-1] == '\r':
+	case i > 0 && c.delim == '\n' && c.data[i-1] == '\r':
 		i--
 	}
 	c.eof = len(c.data) == 0

ext/lines/lines_test.go

@@ -15,13 +15,11 @@ import (
 	_ "github.com/ncruces/go-sqlite3/embed"
 	"github.com/ncruces/go-sqlite3/ext/lines"
 	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
+	"github.com/ncruces/go-sqlite3/vfs/memdb"
 )
 
 func Example() {
-	db, err := driver.Open(":memory:", func(c *sqlite3.Conn) error {
-		lines.Register(c)
-		return nil
-	})
+	db, err := driver.Open("file:/test.db?vfs=memdb", lines.Register)
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -69,11 +67,9 @@ func Example() {
 
 func Test_lines(t *testing.T) {
 	t.Parallel()
+	tmp := memdb.TestDB(t)
 
-	db, err := driver.Open(":memory:", func(c *sqlite3.Conn) error {
-		lines.Register(c)
-		return nil
-	})
+	db, err := driver.Open(tmp, lines.Register)
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -102,11 +98,9 @@ func Test_lines(t *testing.T) {
 
 func Test_lines_error(t *testing.T) {
 	t.Parallel()
+	tmp := memdb.TestDB(t)
 
-	db, err := driver.Open(":memory:", func(c *sqlite3.Conn) error {
-		lines.Register(c)
-		return nil
-	})
+	db, err := driver.Open(tmp, lines.Register)
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -129,11 +123,9 @@ func Test_lines_error(t *testing.T) {
 
 func Test_lines_read(t *testing.T) {
 	t.Parallel()
+	tmp := memdb.TestDB(t)
 
-	db, err := driver.Open(":memory:", func(c *sqlite3.Conn) error {
-		lines.Register(c)
-		return nil
-	})
+	db, err := driver.Open(tmp, lines.Register)
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -163,17 +155,15 @@ func Test_lines_read(t *testing.T) {
 
 func Test_lines_test(t *testing.T) {
 	t.Parallel()
+	tmp := memdb.TestDB(t)
 
-	db, err := driver.Open(":memory:", func(c *sqlite3.Conn) error {
-		lines.Register(c)
-		return nil
-	})
+	db, err := driver.Open(tmp, lines.Register)
 	if err != nil {
 		log.Fatal(err)
 	}
 	defer db.Close()
 
-	rows, err := db.Query(`SELECT rowid, line FROM lines_read(?)`, "lines_test.go")
+	rows, err := db.Query(`SELECT rowid, line FROM lines_read(?, '}')`, "lines_test.go")
 	if errors.Is(err, os.ErrNotExist) {
 		t.Skip(err)
 	}

ext/pivot/pivot.go

@@ -9,11 +9,12 @@ import (
 	"strings"
 
 	"github.com/ncruces/go-sqlite3"
+	"github.com/ncruces/go-sqlite3/internal/util"
 )
 
 // Register registers the pivot virtual table.
-func Register(db *sqlite3.Conn) {
-	sqlite3.CreateModule(db, "pivot", declare, declare)
+func Register(db *sqlite3.Conn) error {
+	return sqlite3.CreateModule(db, "pivot", declare, declare)
 }
 
 type table struct {
@@ -24,15 +25,15 @@ type table struct {
 	cols []*sqlite3.Value
 }
 
-func declare(db *sqlite3.Conn, _, _, _ string, arg ...string) (_ *table, err error) {
+func declare(db *sqlite3.Conn, _, _, _ string, arg ...string) (ret *table, err error) {
 	if len(arg) != 3 {
 		return nil, fmt.Errorf("pivot: wrong number of arguments")
 	}
 
-	table := &table{db: db}
+	t := &table{db: db}
 	defer func() {
-		if err != nil {
-			table.Close()
+		if ret == nil {
+			t.Close()
 		}
 	}()
 
@@ -41,17 +42,17 @@ func declare(db *sqlite3.Conn, _, _, _ string, arg ...string) (_ *table, err err
 	create.WriteString("CREATE TABLE x(")
 
 	// Row key query.
-	table.scan = "SELECT * FROM\n" + arg[0]
-	stmt, _, err := db.Prepare(table.scan)
+	t.scan = "SELECT * FROM\n" + arg[0]
+	stmt, _, err := db.Prepare(t.scan)
 	if err != nil {
 		return nil, err
 	}
 	defer stmt.Close()
 
-	table.keys = make([]string, stmt.ColumnCount())
-	for i := range table.keys {
+	t.keys = make([]string, stmt.ColumnCount())
+	for i := range t.keys {
 		name := sqlite3.QuoteIdentifier(stmt.ColumnName(i))
-		table.keys[i] = name
+		t.keys[i] = name
 		create.WriteString(sep)
 		create.WriteString(name)
 		sep = ","
@@ -65,28 +66,28 @@ func declare(db *sqlite3.Conn, _, _, _ string, arg ...string) (_ *table, err err
 	}
 
 	if stmt.ColumnCount() != 2 {
-		return nil, errors.New("pivot: column definition query expects 2 result columns")
+		return nil, util.ErrorString("pivot: column definition query expects 2 result columns")
 	}
 	for stmt.Step() {
 		name := sqlite3.QuoteIdentifier(stmt.ColumnText(1))
-		table.cols = append(table.cols, stmt.ColumnValue(0).Dup())
+		t.cols = append(t.cols, stmt.ColumnValue(0).Dup())
 		create.WriteString(",")
 		create.WriteString(name)
 	}
 	stmt.Close()
 
 	// Pivot cell query.
-	table.cell = "SELECT * FROM\n" + arg[2]
-	stmt, _, err = db.Prepare(table.cell)
+	t.cell = "SELECT * FROM\n" + arg[2]
+	stmt, _, err = db.Prepare(t.cell)
 	if err != nil {
 		return nil, err
 	}
 
 	if stmt.ColumnCount() != 1 {
-		return nil, errors.New("pivot: cell query expects 1 result columns")
+		return nil, util.ErrorString("pivot: cell query expects 1 result columns")
 	}
-	if stmt.BindCount() != len(table.keys)+1 {
-		return nil, fmt.Errorf("pivot: cell query expects %d bound parameters", len(table.keys)+1)
+	if stmt.BindCount() != len(t.keys)+1 {
+		return nil, fmt.Errorf("pivot: cell query expects %d bound parameters", len(t.keys)+1)
 	}
 
 	create.WriteByte(')')
@@ -94,14 +95,15 @@ func declare(db *sqlite3.Conn, _, _, _ string, arg ...string) (_ *table, err err
 	if err != nil {
 		return nil, err
 	}
-	return table, nil
+	return t, nil
 }
 
 func (t *table) Close() error {
-	for i := range t.cols {
-		t.cols[i].Close()
+	var errs []error
+	for _, c := range t.cols {
+		errs = append(errs, c.Close())
 	}
-	return nil
+	return errors.Join(errs...)
 }
 
 func (t *table) BestIndex(idx *sqlite3.IndexInfo) error {
@@ -205,7 +207,7 @@ func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
 func (c *cursor) Next() error {
 	if c.scan.Step() {
 		count := c.scan.ColumnCount()
-		for i := 0; i < count; i++ {
+		for i := range count {
 			err := c.cell.BindValue(i+1, c.scan.ColumnValue(i))
 			if err != nil {
 				return err
@@ -224,7 +226,7 @@ func (c *cursor) RowID() (int64, error) {
 	return c.rowID, nil
 }
 
-func (c *cursor) Column(ctx *sqlite3.Context, col int) error {
+func (c *cursor) Column(ctx sqlite3.Context, col int) error {
 	count := c.scan.ColumnCount()
 	if col < count {
 		ctx.ResultValue(c.scan.ColumnValue(col))

ext/pivot/pivot_test.go

@@ -14,14 +14,14 @@ import (
 
 // https://antonz.org/sqlite-pivot-table/
 func Example() {
+	sqlite3.AutoExtension(pivot.Register)
+
 	db, err := sqlite3.Open(":memory:")
 	if err != nil {
 		log.Fatal(err)
 	}
 	defer db.Close()
 
-	pivot.Register(db)
-
 	err = db.Exec(`
 		CREATE TABLE sales(product TEXT, year INT, income DECIMAL);
 		INSERT INTO  sales(product, year, income) VALUES
@@ -83,6 +83,11 @@ func Example() {
 	// gamma   80      75      78      80
 }
 
+func TestMain(m *testing.M) {
+	sqlite3.AutoExtension(pivot.Register)
+	m.Run()
+}
+
 func TestRegister(t *testing.T) {
 	t.Parallel()
 
@@ -92,8 +97,6 @@ func TestRegister(t *testing.T) {
 	}
 	defer db.Close()
 
-	pivot.Register(db)
-
 	err = db.Exec(`
 		CREATE TABLE r AS
 			SELECT 1 id UNION SELECT 2 UNION SELECT 3;
@@ -142,6 +145,11 @@ func TestRegister(t *testing.T) {
 			t.Errorf("got %d, want 3", got)
 		}
 	}
+
+	err = db.Exec(`ALTER TABLE v_x RENAME TO v_y`)
+	if err != nil {
+		t.Fatal(err)
+	}
 }
 
 func TestRegister_errors(t *testing.T) {
@@ -153,8 +161,6 @@ func TestRegister_errors(t *testing.T) {
 	}
 	defer db.Close()
 
-	pivot.Register(db)
-
 	err = db.Exec(`CREATE VIRTUAL TABLE pivot USING pivot()`)
 	if err == nil {
 		t.Fatal("want error")

ext/regexp/regexp.go

@@ -0,0 +1,292 @@
+// Package regexp provides additional regular expression functions.
+//
+// It provides the following Unicode aware functions:
+//   - regexp_like(text, pattern),
+//   - regexp_count(text, pattern [, start]),
+//   - regexp_instr(text, pattern [, start [, N [, endoption [, subexpr ]]]]),
+//   - regexp_substr(text, pattern [, start [, N [, subexpr ]]]),
+//   - regexp_replace(text, pattern, replacement [, start [, N ]]),
+//   - and a REGEXP operator.
+//
+// The implementation uses Go [regexp/syntax] for regular expressions.
+//
+// https://github.com/nalgeon/sqlean/blob/main/docs/regexp.md
+package regexp
+
+import (
+	"errors"
+	"regexp"
+	"regexp/syntax"
+	"strings"
+	"unicode/utf8"
+
+	"github.com/ncruces/go-sqlite3"
+)
+
+// Register registers Unicode aware functions for a database connection.
+func Register(db *sqlite3.Conn) error {
+	const flags = sqlite3.DETERMINISTIC | sqlite3.INNOCUOUS
+	return errors.Join(
+		db.CreateFunction("regexp", 2, flags, regex),
+		db.CreateFunction("regexp_like", 2, flags, regexLike),
+		db.CreateFunction("regexp_count", 2, flags, regexCount),
+		db.CreateFunction("regexp_count", 3, flags, regexCount),
+		db.CreateFunction("regexp_instr", 2, flags, regexInstr),
+		db.CreateFunction("regexp_instr", 3, flags, regexInstr),
+		db.CreateFunction("regexp_instr", 4, flags, regexInstr),
+		db.CreateFunction("regexp_instr", 5, flags, regexInstr),
+		db.CreateFunction("regexp_instr", 6, flags, regexInstr),
+		db.CreateFunction("regexp_substr", 2, flags, regexSubstr),
+		db.CreateFunction("regexp_substr", 3, flags, regexSubstr),
+		db.CreateFunction("regexp_substr", 4, flags, regexSubstr),
+		db.CreateFunction("regexp_substr", 5, flags, regexSubstr),
+		db.CreateFunction("regexp_replace", 3, flags, regexReplace),
+		db.CreateFunction("regexp_replace", 4, flags, regexReplace),
+		db.CreateFunction("regexp_replace", 5, flags, regexReplace))
+}
+
+// GlobPrefix returns a GLOB for a regular expression
+// appropriate to take advantage of the [LIKE optimization]
+// in a query such as:
+//
+//	SELECT column WHERE column GLOB :glob_prefix AND column REGEXP :regexp
+//
+// [LIKE optimization]: https://sqlite.org/optoverview.html#the_like_optimization
+func GlobPrefix(expr string) string {
+	re, err := syntax.Parse(expr, syntax.Perl)
+	if err != nil {
+		return "" // no match possible
+	}
+	prog, err := syntax.Compile(re.Simplify())
+	if err != nil {
+		return "" // notest
+	}
+
+	i := &prog.Inst[prog.Start]
+
+	var empty syntax.EmptyOp
+loop1:
+	for {
+		switch i.Op {
+		case syntax.InstFail:
+			return "" // notest
+		case syntax.InstCapture, syntax.InstNop:
+			// skip
+		case syntax.InstEmptyWidth:
+			empty |= syntax.EmptyOp(i.Arg)
+		default:
+			break loop1
+		}
+		i = &prog.Inst[i.Out]
+	}
+	if empty&syntax.EmptyBeginText == 0 {
+		return "*" // not anchored
+	}
+
+	var glob strings.Builder
+loop2:
+	for {
+		switch i.Op {
+		case syntax.InstFail:
+			return "" // notest
+		case syntax.InstCapture, syntax.InstEmptyWidth, syntax.InstNop:
+			// skip
+		case syntax.InstRune, syntax.InstRune1:
+			if len(i.Rune) != 1 || syntax.Flags(i.Arg)&syntax.FoldCase != 0 {
+				break loop2
+			}
+			switch r := i.Rune[0]; r {
+			case '*', '?', '[', utf8.RuneError:
+				break loop2
+			default:
+				glob.WriteRune(r)
+			}
+		default:
+			break loop2
+		}
+		i = &prog.Inst[i.Out]
+	}
+
+	glob.WriteByte('*')
+	return glob.String()
+}
+
+func load(ctx sqlite3.Context, i int, expr string) (*regexp.Regexp, error) {
+	re, ok := ctx.GetAuxData(i).(*regexp.Regexp)
+	if !ok {
+		r, err := regexp.Compile(expr)
+		if err != nil {
+			return nil, err
+		}
+		re = r
+		ctx.SetAuxData(0, r)
+	}
+	return re, nil
+}
+
+func regex(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	_ = arg[1] // bounds check
+	re, err := load(ctx, 0, arg[0].Text())
+	if err != nil {
+		ctx.ResultError(err)
+		return // notest
+	}
+	text := arg[1].RawText()
+	ctx.ResultBool(re.Match(text))
+}
+
+func regexLike(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	re, err := load(ctx, 1, arg[1].Text())
+	if err != nil {
+		ctx.ResultError(err)
+		return // notest
+	}
+
+	text := arg[0].RawText()
+	ctx.ResultBool(re.Match(text))
+}
+
+func regexCount(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	re, err := load(ctx, 1, arg[1].Text())
+	if err != nil {
+		ctx.ResultError(err)
+		return // notest
+	}
+
+	text := arg[0].RawText()
+	if len(arg) > 2 {
+		pos := arg[2].Int()
+		text = text[skip(text, pos):]
+	}
+	ctx.ResultInt(len(re.FindAll(text, -1)))
+}
+
+func regexSubstr(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	re, err := load(ctx, 1, arg[1].Text())
+	if err != nil {
+		ctx.ResultError(err)
+		return // notest
+	}
+
+	text := arg[0].RawText()
+	var pos, n, subexpr int
+	if len(arg) > 2 {
+		pos = arg[2].Int()
+	}
+	if len(arg) > 3 {
+		n = arg[3].Int()
+	}
+	if len(arg) > 4 {
+		subexpr = arg[4].Int()
+	}
+
+	loc := regexFind(re, text, pos, n, subexpr)
+	if loc != nil {
+		ctx.ResultRawText(text[loc[0]:loc[1]])
+	}
+}
+
+func regexInstr(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	re, err := load(ctx, 1, arg[1].Text())
+	if err != nil {
+		ctx.ResultError(err)
+		return // notest
+	}
+
+	text := arg[0].RawText()
+	var pos, n, end, subexpr int
+	if len(arg) > 2 {
+		pos = arg[2].Int()
+	}
+	if len(arg) > 3 {
+		n = arg[3].Int()
+	}
+	if len(arg) > 4 && arg[4].Bool() {
+		end = 1
+	}
+	if len(arg) > 5 {
+		subexpr = arg[5].Int()
+	}
+
+	loc := regexFind(re, text, pos, n, subexpr)
+	if loc != nil {
+		ctx.ResultInt(loc[end] + 1)
+	}
+}
+
+func regexReplace(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	_ = arg[2] // bounds check
+
+	re, err := load(ctx, 1, arg[1].Text())
+	if err != nil {
+		ctx.ResultError(err)
+		return // notest
+	}
+
+	text := arg[0].RawText()
+	repl := arg[2].RawText()
+	var pos, n int
+	if len(arg) > 3 {
+		pos = arg[3].Int()
+	}
+	if len(arg) > 4 {
+		n = arg[4].Int()
+	}
+
+	res := text
+	pos = skip(text, pos)
+	if n > 0 {
+		all := re.FindAllSubmatchIndex(text[pos:], n)
+		if n <= len(all) {
+			loc := all[n-1]
+			res = text[:pos+loc[0]]
+			res = re.Expand(res, repl, text[pos:], loc)
+			res = append(res, text[pos+loc[1]:]...)
+		}
+	} else {
+		res = append(text[:pos], re.ReplaceAll(text[pos:], repl)...)
+	}
+	ctx.ResultRawText(res)
+}
+
+func regexFind(re *regexp.Regexp, text []byte, pos, n, subexpr int) (loc []int) {
+	pos = skip(text, pos)
+	text = text[pos:]
+
+	if n <= 1 {
+		if subexpr == 0 {
+			loc = re.FindIndex(text)
+		} else {
+			loc = re.FindSubmatchIndex(text)
+		}
+	} else {
+		if subexpr == 0 {
+			all := re.FindAllIndex(text, n)
+			if n <= len(all) {
+				loc = all[n-1]
+			}
+		} else {
+			all := re.FindAllSubmatchIndex(text, n)
+			if n <= len(all) {
+				loc = all[n-1]
+			}
+		}
+	}
+
+	if 2+2*subexpr <= len(loc) {
+		loc = loc[2*subexpr : 2+2*subexpr]
+		loc[0] += pos
+		loc[1] += pos
+		return loc
+	}
+	return nil
+}
+
+func skip(text []byte, start int) int {
+	for pos := range string(text) {
+		if start--; start <= 0 {
+			return pos
+		}
+	}
+	return len(text)
+}

ext/regexp/regexp_test.go

@@ -0,0 +1,163 @@
+package regexp
+
+import (
+	"database/sql"
+	"regexp"
+	"strings"
+	"testing"
+
+	"github.com/ncruces/go-sqlite3/driver"
+	_ "github.com/ncruces/go-sqlite3/embed"
+	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
+	"github.com/ncruces/go-sqlite3/vfs/memdb"
+)
+
+func TestRegister(t *testing.T) {
+	t.Parallel()
+	tmp := memdb.TestDB(t)
+
+	db, err := driver.Open(tmp, Register)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	tests := []struct {
+		test string
+		want string
+	}{
+		{`'Hello' REGEXP 'elo'`, "0"},
+		{`'Hello' REGEXP 'ell'`, "1"},
+		{`'Hello' REGEXP 'el.'`, "1"},
+		{`regexp_like('Hello', 'elo')`, "0"},
+		{`regexp_like('Hello', 'ell')`, "1"},
+		{`regexp_like('Hello', 'el.')`, "1"},
+		{`regexp_count('Hello', 'l')`, "2"},
+		{`regexp_instr('Hello', 'el.')`, "2"},
+		{`regexp_instr('Hello', '.', 6)`, ""},
+		{`regexp_substr('Hello', 'el.')`, "ell"},
+		{`regexp_replace('Hello', 'llo', 'll')`, "Hell"},
+		// https://www.postgresql.org/docs/current/functions-matching.html
+		{`regexp_count('ABCABCAXYaxy', 'A.')`, "3"},
+		{`regexp_count('ABCABCAXYaxy', '(?i)A.', 1)`, "4"},
+		{`regexp_instr('number of your street, town zip, FR', '[^,]+', 1, 2)`, "23"},
+		{`regexp_instr('ABCDEFGHI', '(?i)(c..)(...)', 1, 1, 0, 2)`, "6"},
+		{`regexp_substr('number of your street, town zip, FR', '[^,]+', 1, 2)`, " town zip"},
+		{`regexp_substr('ABCDEFGHI', '(?i)(c..)(...)', 1, 1, 2)`, "FGH"},
+		{`regexp_replace('foobarbaz', 'b..', 'X', 1, 1)`, "fooXbaz"},
+		{`regexp_replace('foobarbaz', 'b..', 'X')`, "fooXX"},
+		{`regexp_replace('foobarbaz', 'b(..)', 'X${1}Y')`, "fooXarYXazY"},
+		{`regexp_replace('A PostgreSQL function', '(?i)a|e|i|o|u', 'X', 1, 0)`, "X PXstgrXSQL fXnctXXn"},
+		{`regexp_replace('A PostgreSQL function', '(?i)a|e|i|o|u', 'X', 1, 3)`, "A PostgrXSQL function"},
+		// https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlrf/REGEXP_COUNT.html
+		{`regexp_count('123123123123123', '(12)3', 1)`, "5"},
+		{`regexp_count('123123123123', '123', 3)`, "3"},
+		{`regexp_instr('500 Oracle Parkway, Redwood Shores, CA', '[^ ]+', 1, 6)`, "37"},
+		{`regexp_instr('500 Oracle Parkway, Redwood Shores, CA', '(?i)[s|r|p][[:alpha:]]{6}', 3, 2, 1)`, "28"},
+		{`regexp_instr('1234567890', '(123)(4(56)(78))', 1, 1, 0, 1)`, "1"},
+		{`regexp_instr('1234567890', '(123)(4(56)(78))', 1, 1, 0, 2)`, "4"},
+		{`regexp_instr('1234567890', '(123)(4(56)(78))', 1, 1, 0, 4)`, "7"},
+		{`regexp_substr('500 Oracle Parkway, Redwood Shores, CA', ',[^,]+,')`, ", Redwood Shores,"},
+		{`regexp_substr('http://www.example.com/products', 'http://([[:alnum:]]+\.?){3,4}/?')`, "http://www.example.com/"},
+		{`regexp_substr('1234567890', '(123)(4(56)(78))', 1, 1, 1)`, "123"},
+		{`regexp_substr('1234567890', '(123)(4(56)(78))', 1, 1, 4)`, "78"},
+		{`regexp_substr('123123123123', '1(.)3', 3, 2, 1)`, "2"},
+		{`regexp_replace('500   Oracle     Parkway,    Redwood  Shores, CA', '( ){2,}', ' ')`, "500 Oracle Parkway, Redwood Shores, CA"},
+	}
+
+	for _, tt := range tests {
+		var got sql.NullString
+		err := db.QueryRow(`SELECT ` + tt.test).Scan(&got)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got.String != tt.want {
+			t.Errorf("got %q, want %q", got.String, tt.want)
+		}
+	}
+}
+
+func TestRegister_errors(t *testing.T) {
+	t.Parallel()
+	tmp := memdb.TestDB(t)
+
+	db, err := driver.Open(tmp, Register)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	tests := []string{
+		`'' REGEXP ?`,
+		`regexp_like('', ?)`,
+		`regexp_count('', ?)`,
+		`regexp_instr('', ?)`,
+		`regexp_substr('', ?)`,
+		`regexp_replace('', ?, '')`,
+	}
+
+	for _, tt := range tests {
+		err := db.QueryRow(`SELECT `+tt, `\`).Scan(nil)
+		if err == nil {
+			t.Fatal("want error")
+		}
+	}
+}
+
+func TestGlobPrefix(t *testing.T) {
+	tests := []struct {
+		re   string
+		want string
+	}{
+		{`[`, ""},
+		{``, "*"},
+		{`^`, "*"},
+		{`a`, "*"},
+		{`ab`, "*"},
+		{`^a`, "a*"},
+		{`^a*`, "*"},
+		{`^a+`, "a*"},
+		{`^ab*`, "a*"},
+		{`^ab+`, "ab*"},
+		{`^a\?b`, "a*"},
+		{`^[a-z]`, "*"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.re, func(t *testing.T) {
+			if got := GlobPrefix(tt.re); got != tt.want {
+				t.Errorf("GlobPrefix(%v) = %v, want %v", tt.re, got, tt.want)
+			}
+		})
+	}
+}
+
+func FuzzGlobPrefix(f *testing.F) {
+	f.Add(``, ``)
+	f.Add(`[`, ``)
+	f.Add(`^`, ``)
+	f.Add(`a`, `a`)
+	f.Add(`ab`, `b`)
+	f.Add(`^a`, `a`)
+	f.Add(`^a*`, `ab`)
+	f.Add(`^a+`, `ab`)
+	f.Add(`^ab*`, `ab`)
+	f.Add(`^ab+`, `ab`)
+	f.Add(`^a\?b`, `ab`)
+	f.Add(`^[a-z]`, `ab`)
+
+	f.Fuzz(func(t *testing.T, lit, str string) {
+		re, err := regexp.Compile(lit)
+		if err != nil {
+			t.SkipNow()
+		}
+		if re.MatchString(str) {
+			prefix, ok := strings.CutSuffix(GlobPrefix(lit), "*")
+			if !ok {
+				t.Fatalf("missing * after %q for %q with %q", prefix, lit, str)
+			}
+			if !strings.HasPrefix(str, prefix) {
+				t.Fatalf("missing prefix %q for %q with %q", prefix, lit, str)
+			}
+		}
+	})
+}

ext/serdes/serdes.go

@@ -0,0 +1,140 @@
+// Package serdes provides functions to (de)serialize databases.
+package serdes
+
+import (
+	"io"
+
+	"github.com/ncruces/go-sqlite3"
+	"github.com/ncruces/go-sqlite3/vfs"
+)
+
+const vfsName = "github.com/ncruces/go-sqlite3/ext/serdes.sliceVFS"
+
+func init() {
+	vfs.Register(vfsName, sliceVFS{})
+}
+
+var fileToOpen = make(chan *sliceFile, 1)
+
+// Serialize backs up a database into a byte slice.
+//
+// https://sqlite.org/c3ref/serialize.html
+func Serialize(db *sqlite3.Conn, schema string) ([]byte, error) {
+	var file sliceFile
+	fileToOpen <- &file
+	err := db.Backup(schema, "file:serdes.db?vfs="+vfsName)
+	return file.data, err
+}
+
+// Deserialize restores a database from a byte slice,
+// DESTROYING any contents previously stored in schema.
+//
+// To non-destructively open a database from a byte slice,
+// consider alternatives like the ["reader"] or ["memdb"] VFSes.
+//
+// This differs from the similarly named SQLite API
+// in that it DOES NOT disconnect from schema
+// to reopen as an in-memory database.
+//
+// https://sqlite.org/c3ref/deserialize.html
+//
+// ["memdb"]: https://pkg.go.dev/github.com/ncruces/go-sqlite3/vfs/memdb
+// ["reader"]: https://pkg.go.dev/github.com/ncruces/go-sqlite3/vfs/readervfs
+func Deserialize(db *sqlite3.Conn, schema string, data []byte) error {
+	fileToOpen <- &sliceFile{data}
+	return db.Restore(schema, "file:serdes.db?vfs="+vfsName)
+}
+
+type sliceVFS struct{}
+
+func (sliceVFS) Open(name string, flags vfs.OpenFlag) (vfs.File, vfs.OpenFlag, error) {
+	if flags&vfs.OPEN_MAIN_DB == 0 || name != "serdes.db" {
+		return nil, flags, sqlite3.CANTOPEN
+	}
+	select {
+	case file := <-fileToOpen:
+		return file, flags | vfs.OPEN_MEMORY, nil
+	default:
+		return nil, flags, sqlite3.MISUSE
+	}
+}
+
+func (sliceVFS) Delete(name string, dirSync bool) error {
+	// notest // OPEN_MEMORY
+	return sqlite3.IOERR_DELETE
+}
+
+func (sliceVFS) Access(name string, flag vfs.AccessFlag) (bool, error) {
+	return name == "serdes.db", nil
+}
+
+func (sliceVFS) FullPathname(name string) (string, error) {
+	return name, nil
+}
+
+type sliceFile struct{ data []byte }
+
+func (f *sliceFile) ReadAt(b []byte, off int64) (n int, err error) {
+	if d := f.data; off < int64(len(d)) {
+		n = copy(b, d[off:])
+	}
+	if n == 0 {
+		err = io.EOF
+	}
+	return
+}
+
+func (f *sliceFile) WriteAt(b []byte, off int64) (n int, err error) {
+	if d := f.data; off > int64(len(d)) {
+		f.data = append(d, make([]byte, off-int64(len(d)))...)
+	}
+	d := append(f.data[:off], b...)
+	if len(d) > len(f.data) {
+		f.data = d
+	}
+	return len(b), nil
+}
+
+func (f *sliceFile) Size() (int64, error) {
+	return int64(len(f.data)), nil
+}
+
+func (f *sliceFile) Truncate(size int64) error {
+	if d := f.data; size < int64(len(d)) {
+		f.data = d[:size]
+	}
+	return nil
+}
+
+func (f *sliceFile) SizeHint(size int64) error {
+	if d := f.data; size > int64(len(d)) {
+		f.data = append(d, make([]byte, size-int64(len(d)))...)
+	}
+	return nil
+}
+
+func (*sliceFile) Close() error { return nil }
+
+func (*sliceFile) Sync(flag vfs.SyncFlag) error { return nil }
+
+func (*sliceFile) Lock(lock vfs.LockLevel) error { return nil }
+
+func (*sliceFile) Unlock(lock vfs.LockLevel) error { return nil }
+
+func (*sliceFile) CheckReservedLock() (bool, error) {
+	// notest // OPEN_MEMORY
+	return false, nil
+}
+
+func (*sliceFile) SectorSize() int {
+	// notest // IOCAP_POWERSAFE_OVERWRITE
+	return 0
+}
+
+func (*sliceFile) DeviceCharacteristics() vfs.DeviceCharacteristic {
+	return vfs.IOCAP_ATOMIC |
+		vfs.IOCAP_SAFE_APPEND |
+		vfs.IOCAP_SEQUENTIAL |
+		vfs.IOCAP_POWERSAFE_OVERWRITE |
+		vfs.IOCAP_SUBPAGE_READ
+}

ext/serdes/serdes_test.go

@@ -0,0 +1,87 @@
+package serdes_test
+
+import (
+	"errors"
+	"io"
+	"net/http"
+	"testing"
+
+	"github.com/ncruces/go-sqlite3"
+	_ "github.com/ncruces/go-sqlite3/embed"
+	"github.com/ncruces/go-sqlite3/ext/serdes"
+)
+
+func TestDeserialize(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping in short mode")
+	}
+
+	input, err := httpGet()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	err = serdes.Deserialize(db, "temp", input)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	output, err := serdes.Serialize(db, "temp")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(input) != len(output) {
+		t.Fatal("lengths are different")
+	}
+	for i := range input {
+		// These may be different.
+		switch {
+		case 24 <= i && i < 28:
+			// File change counter.
+			continue
+		case 40 <= i && i < 44:
+			// Schema cookie.
+			continue
+		case 92 <= i && i < 100:
+			// SQLite version that wrote the file.
+			continue
+		}
+		if input[i] != output[i] {
+			t.Errorf("difference at %d: %d %d", i, input[i], output[i])
+		}
+	}
+}
+
+func httpGet() ([]byte, error) {
+	res, err := http.Get("https://raw.githubusercontent.com/jpwhite3/northwind-SQLite3/refs/heads/main/dist/northwind.db")
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	return io.ReadAll(res.Body)
+}
+
+func TestOpen_errors(t *testing.T) {
+	_, err := sqlite3.Open("file:test.db?vfs=github.com/ncruces/go-sqlite3/ext/serdes.sliceVFS")
+	if err == nil {
+		t.Error("want error")
+	}
+	if !errors.Is(err, sqlite3.CANTOPEN) {
+		t.Errorf("got %v, want sqlite3.CANTOPEN", err)
+	}
+
+	_, err = sqlite3.Open("file:serdes.db?vfs=github.com/ncruces/go-sqlite3/ext/serdes.sliceVFS")
+	if err == nil {
+		t.Error("want error")
+	}
+	if !errors.Is(err, sqlite3.MISUSE) {
+		t.Errorf("got %v, want sqlite3.MISUSE", err)
+	}
+}

ext/statement/stmt.go

@@ -14,11 +14,12 @@ import (
 	"unsafe"
 
 	"github.com/ncruces/go-sqlite3"
+	"github.com/ncruces/go-sqlite3/internal/util"
 )
 
 // Register registers the statement virtual table.
-func Register(db *sqlite3.Conn) {
-	sqlite3.CreateModule(db, "statement", declare, declare)
+func Register(db *sqlite3.Conn) error {
+	return sqlite3.CreateModule(db, "statement", declare, declare)
 }
 
 type table struct {
@@ -29,12 +30,12 @@ type table struct {
 
 func declare(db *sqlite3.Conn, _, _, _ string, arg ...string) (*table, error) {
 	if len(arg) != 1 {
-		return nil, errors.New("statement: wrong number of arguments")
+		return nil, util.ErrorString("statement: wrong number of arguments")
 	}
 
 	sql := "SELECT * FROM\n" + arg[0]
 
-	stmt, _, err := db.Prepare(sql)
+	stmt, _, err := db.PrepareFlags(sql, sqlite3.PREPARE_PERSISTENT)
 	if err != nil {
 		return nil, err
 	}
@@ -43,7 +44,7 @@ func declare(db *sqlite3.Conn, _, _, _ string, arg ...string) (*table, error) {
 	var str strings.Builder
 	str.WriteString("CREATE TABLE x(")
 	outputs := stmt.ColumnCount()
-	for i := 0; i < outputs; i++ {
+	for i := range outputs {
 		name := sqlite3.QuoteIdentifier(stmt.ColumnName(i))
 		str.WriteString(sep)
 		str.WriteString(name)
@@ -123,12 +124,11 @@ func (t *table) BestIndex(idx *sqlite3.IndexInfo) error {
 	return nil
 }
 
-func (t *table) Open() (sqlite3.VTabCursor, error) {
+func (t *table) Open() (_ sqlite3.VTabCursor, err error) {
 	stmt := t.stmt
 	if !t.inuse {
 		t.inuse = true
 	} else {
-		var err error
 		stmt, _, err = t.stmt.Conn().Prepare(t.sql)
 		if err != nil {
 			return nil, err
@@ -151,8 +151,9 @@ type cursor struct {
 func (c *cursor) Close() error {
 	if c.stmt == c.table.stmt {
 		c.table.inuse = false
-		c.stmt.ClearBindings()
-		return c.stmt.Reset()
+		return errors.Join(
+			c.stmt.Reset(),
+			c.stmt.ClearBindings())
 	}
 	return c.stmt.Close()
 }
@@ -160,8 +161,10 @@ func (c *cursor) Close() error {
 func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
 	c.arg = arg
 	c.rowID = 0
-	c.stmt.ClearBindings()
-	if err := c.stmt.Reset(); err != nil {
+	err := errors.Join(
+		c.stmt.Reset(),
+		c.stmt.ClearBindings())
+	if err != nil {
 		return err
 	}
 
@@ -202,7 +205,7 @@ func (c *cursor) RowID() (int64, error) {
 	return c.rowID, nil
 }
 
-func (c *cursor) Column(ctx *sqlite3.Context, col int) error {
+func (c *cursor) Column(ctx sqlite3.Context, col int) error {
 	switch outputs := c.stmt.ColumnCount(); {
 	case col < outputs:
 		ctx.ResultValue(c.stmt.ColumnValue(col))

ext/statement/stmt_test.go

@@ -12,14 +12,14 @@ import (
 )
 
 func Example() {
+	sqlite3.AutoExtension(statement.Register)
+
 	db, err := sqlite3.Open(":memory:")
 	if err != nil {
 		log.Fatal(err)
 	}
 	defer db.Close()
 
-	statement.Register(db)
-
 	err = db.Exec(`
 		CREATE VIRTUAL TABLE split_date USING statement((
 			SELECT
@@ -48,6 +48,11 @@ func Example() {
 	// Twosday was 2022-2-22
 }
 
+func TestMain(m *testing.M) {
+	sqlite3.AutoExtension(statement.Register)
+	m.Run()
+}
+
 func TestRegister(t *testing.T) {
 	t.Parallel()
 
@@ -57,8 +62,6 @@ func TestRegister(t *testing.T) {
 	}
 	defer db.Close()
 
-	statement.Register(db)
-
 	err = db.Exec(`
 		CREATE VIRTUAL TABLE arguments USING statement((SELECT ? AS a, ? AS b, ? AS c))
 	`)
@@ -107,8 +110,6 @@ func TestRegister_errors(t *testing.T) {
 	}
 	defer db.Close()
 
-	statement.Register(db)
-
 	err = db.Exec(`CREATE VIRTUAL TABLE split_date USING statement()`)
 	if err == nil {
 		t.Fatal("want error")

ext/stats/boolean.go

@@ -26,21 +26,21 @@ func (b *boolean) Value(ctx sqlite3.Context) {
 }
 
 func (b *boolean) Step(ctx sqlite3.Context, arg ...sqlite3.Value) {
-	if arg[0].Type() == sqlite3.NULL {
-		return
-	}
-	if arg[0].Bool() {
+	a := arg[0]
+	if a.Bool() {
 		b.count++
 	}
-	b.total++
+	if a.Type() != sqlite3.NULL {
+		b.total++
+	}
 }
 
 func (b *boolean) Inverse(ctx sqlite3.Context, arg ...sqlite3.Value) {
-	if arg[0].Type() == sqlite3.NULL {
-		return
-	}
-	if arg[0].Bool() {
+	a := arg[0]
+	if a.Bool() {
 		b.count--
 	}
-	b.total--
+	if a.Type() != sqlite3.NULL {
+		b.total--
+	}
 }

ext/stats/boolean_test.go

@@ -5,7 +5,6 @@ import (
 
 	"github.com/ncruces/go-sqlite3"
 	_ "github.com/ncruces/go-sqlite3/embed"
-	"github.com/ncruces/go-sqlite3/ext/stats"
 	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
 )
 
@@ -18,8 +17,6 @@ func TestRegister_boolean(t *testing.T) {
 	}
 	defer db.Close()
 
-	stats.Register(db)
-
 	err = db.Exec(`CREATE TABLE data (x)`)
 	if err != nil {
 		t.Fatal(err)

ext/stats/kahan.go

@@ -0,0 +1,19 @@
+package stats
+
+// https://en.wikipedia.org/wiki/Kahan_summation_algorithm
+
+type kahan struct{ hi, lo float64 }
+
+func (k *kahan) add(x float64) {
+	y := k.lo + x
+	t := k.hi + y
+	k.lo = y - (t - k.hi)
+	k.hi = t
+}
+
+func (k *kahan) sub(x float64) {
+	y := k.lo - x
+	t := k.hi + y
+	k.lo = y - (t - k.hi)
+	k.hi = t
+}

ext/stats/mode.go

@@ -0,0 +1,112 @@
+package stats
+
+import (
+	"unsafe"
+
+	"github.com/ncruces/go-sqlite3"
+)
+
+func newMode() sqlite3.AggregateFunction {
+	return &mode{}
+}
+
+type mode struct {
+	ints  counter[int64]
+	reals counter[float64]
+	texts counter[string]
+	blobs counter[string]
+}
+
+func (m mode) Value(ctx sqlite3.Context) {
+	var (
+		max = 0
+		typ = sqlite3.NULL
+		i64 int64
+		f64 float64
+		str string
+	)
+	for k, v := range m.ints {
+		if v > max || v == max && k < i64 {
+			typ = sqlite3.INTEGER
+			max = v
+			i64 = k
+		}
+	}
+	f64 = float64(i64)
+	for k, v := range m.reals {
+		if v > max || v == max && k < f64 {
+			typ = sqlite3.FLOAT
+			max = v
+			f64 = k
+		}
+	}
+	for k, v := range m.texts {
+		if v > max || v == max && typ == sqlite3.TEXT && k < str {
+			typ = sqlite3.TEXT
+			max = v
+			str = k
+		}
+	}
+	for k, v := range m.blobs {
+		if v > max || v == max && typ == sqlite3.BLOB && k < str {
+			typ = sqlite3.BLOB
+			max = v
+			str = k
+		}
+	}
+	switch typ {
+	case sqlite3.INTEGER:
+		ctx.ResultInt64(i64)
+	case sqlite3.FLOAT:
+		ctx.ResultFloat(f64)
+	case sqlite3.TEXT:
+		ctx.ResultText(str)
+	case sqlite3.BLOB:
+		ctx.ResultBlob(unsafe.Slice(unsafe.StringData(str), len(str)))
+	}
+}
+
+func (b *mode) Step(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	switch arg[0].Type() {
+	case sqlite3.INTEGER:
+		b.ints.add(arg[0].Int64())
+	case sqlite3.FLOAT:
+		b.reals.add(arg[0].Float())
+	case sqlite3.TEXT:
+		b.texts.add(arg[0].Text())
+	case sqlite3.BLOB:
+		b.blobs.add(string(arg[0].RawBlob()))
+	}
+}
+
+func (b *mode) Inverse(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	switch arg[0].Type() {
+	case sqlite3.INTEGER:
+		b.ints.del(arg[0].Int64())
+	case sqlite3.FLOAT:
+		b.reals.del(arg[0].Float())
+	case sqlite3.TEXT:
+		b.texts.del(arg[0].Text())
+	case sqlite3.BLOB:
+		b.blobs.del(string(arg[0].RawBlob()))
+	}
+}
+
+type counter[T comparable] map[T]int
+
+func (c *counter[T]) add(k T) {
+	if (*c) == nil {
+		(*c) = make(counter[T])
+	}
+	(*c)[k]++
+}
+
+func (c counter[T]) del(k T) {
+	switch n := c[k]; n {
+	default:
+		c[k] = n - 1
+	case 1:
+		delete(c, k)
+	case 0:
+	}
+}

ext/stats/mode_test.go

@@ -0,0 +1,85 @@
+package stats_test
+
+import (
+	"testing"
+
+	"github.com/ncruces/go-sqlite3"
+	_ "github.com/ncruces/go-sqlite3/embed"
+	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
+)
+
+func TestRegister_mode(t *testing.T) {
+	t.Parallel()
+
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	stmt, _, err := db.Prepare(`SELECT mode(column1) FROM (VALUES (NULL), (1), (NULL), (2), (NULL), (3), (3))`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if stmt.Step() {
+		if got := stmt.ColumnInt(0); got != 3 {
+			t.Errorf("got %v, want 3", got)
+		}
+	}
+	stmt.Close()
+
+	stmt, _, err = db.Prepare(`SELECT mode(column1) FROM (VALUES (1), (1), (2), (2), (3))`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if stmt.Step() {
+		if got := stmt.ColumnInt(0); got != 1 {
+			t.Errorf("got %v, want 1", got)
+		}
+	}
+	stmt.Close()
+
+	stmt, _, err = db.Prepare(`SELECT mode(column1) FROM (VALUES (0.5), (1), (2.5), (2), (2.5))`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if stmt.Step() {
+		if got := stmt.ColumnFloat(0); got != 2.5 {
+			t.Errorf("got %v, want 2.5", got)
+		}
+	}
+	stmt.Close()
+
+	stmt, _, err = db.Prepare(`SELECT mode(column1) FROM (VALUES ('red'), ('green'), ('blue'), ('red'))`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if stmt.Step() {
+		if got := stmt.ColumnText(0); got != "red" {
+			t.Errorf("got %q, want red", got)
+		}
+	}
+	stmt.Close()
+
+	stmt, _, err = db.Prepare(`SELECT mode(column1) FROM (VALUES (X'cafebabe'), ('green'), ('blue'), (X'cafebabe'))`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if stmt.Step() {
+		if got := stmt.ColumnText(0); got != "\xca\xfe\xba\xbe" {
+			t.Errorf("got %q, want cafebabe", got)
+		}
+	}
+	stmt.Close()
+
+	stmt, _, err = db.Prepare(`
+		SELECT mode(column1) OVER (ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
+		FROM (VALUES (1), (1), (2.5), ('blue'), (X'cafebabe'), (1), (1))
+	`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for stmt.Step() {
+	}
+	stmt.Close()
+}

ext/stats/moments.go

@@ -0,0 +1,101 @@
+package stats
+
+import "math"
+
+// Fisher–Pearson skewness and kurtosis using
+// Terriberry's algorithm with Kahan summation:
+// https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Higher-order_statistics
+
+type moments struct {
+	m1, m2, m3, m4 kahan
+	n              int64
+}
+
+func (m moments) mean() float64 {
+	return m.m1.hi
+}
+
+func (m moments) var_pop() float64 {
+	return m.m2.hi / float64(m.n)
+}
+
+func (m moments) var_samp() float64 {
+	return m.m2.hi / float64(m.n-1) // Bessel's correction
+}
+
+func (m moments) stddev_pop() float64 {
+	return math.Sqrt(m.var_pop())
+}
+
+func (m moments) stddev_samp() float64 {
+	return math.Sqrt(m.var_samp())
+}
+
+func (m moments) skewness_pop() float64 {
+	m2 := m.m2.hi
+	if div := m2 * m2 * m2; div != 0 {
+		return m.m3.hi * math.Sqrt(float64(m.n)/div)
+	}
+	return math.NaN()
+}
+
+func (m moments) skewness_samp() float64 {
+	n := m.n
+	// https://mathworks.com/help/stats/skewness.html#f1132178
+	return m.skewness_pop() * math.Sqrt(float64(n*(n-1))) / float64(n-2)
+}
+
+func (m moments) kurtosis_pop() float64 {
+	return m.raw_kurtosis_pop() - 3
+}
+
+func (m moments) raw_kurtosis_pop() float64 {
+	m2 := m.m2.hi
+	if div := m2 * m2; div != 0 {
+		return m.m4.hi * float64(m.n) / div
+	}
+	return math.NaN()
+}
+
+func (m moments) kurtosis_samp() float64 {
+	n := m.n
+	k := math.FMA(m.raw_kurtosis_pop(), float64(n+1), float64(3-3*n))
+	return k * float64(n-1) / float64((n-2)*(n-3))
+}
+
+func (m moments) raw_kurtosis_samp() float64 {
+	n := m.n
+	// https://mathworks.com/help/stats/kurtosis.html#f4975293
+	k := math.FMA(m.raw_kurtosis_pop(), float64(n+1), float64(3-3*n))
+	return math.FMA(k, float64(n-1)/float64((n-2)*(n-3)), 3)
+}
+
+func (m *moments) enqueue(x float64) {
+	n := m.n + 1
+	m.n = n
+	d1 := x - m.m1.hi - m.m1.lo
+	dn := d1 / float64(n)
+	d2 := dn * dn
+	t1 := d1 * dn * float64(n-1)
+	m.m4.add(t1*d2*float64(n*n-3*n+3) + 6*d2*m.m2.hi - 4*dn*m.m3.hi)
+	m.m3.add(t1*dn*float64(n-2) - 3*dn*m.m2.hi)
+	m.m2.add(t1)
+	m.m1.add(dn)
+}
+
+func (m *moments) dequeue(x float64) {
+	n := m.n - 1
+	if n <= 0 {
+		*m = moments{}
+		return
+	}
+	m.n = n
+	d1 := x - m.m1.hi - m.m1.lo
+	dn := d1 / float64(n)
+	d2 := dn * dn
+	t1 := d1 * dn * float64(n+1)
+	m.m4.sub(t1*d2*float64(n*n+3*n+3) - 6*d2*m.m2.hi - 4*dn*m.m3.hi)
+	m.m3.sub(t1*dn*float64(n+2) - 3*dn*m.m2.hi)
+	m.m2.sub(t1)
+	m.m1.sub(dn)
+}

ext/stats/moments_test.go

@@ -0,0 +1,87 @@
+package stats
+
+import (
+	"math"
+	"testing"
+)
+
+func Test_moments(t *testing.T) {
+	t.Parallel()
+
+	var s1 moments
+	s1.enqueue(1)
+	s1.dequeue(1)
+	if !math.IsNaN(s1.skewness_pop()) {
+		t.Errorf("want NaN")
+	}
+	if !math.IsNaN(s1.raw_kurtosis_pop()) {
+		t.Errorf("want NaN")
+	}
+
+	s1.enqueue(+0.5377)
+	s1.enqueue(+1.8339)
+	s1.enqueue(-2.2588)
+	s1.enqueue(+0.8622)
+	s1.enqueue(+0.3188)
+	s1.enqueue(-1.3077)
+	s1.enqueue(-0.4336)
+	s1.enqueue(+0.3426)
+	s1.enqueue(+3.5784)
+	s1.enqueue(+2.7694)
+
+	if got := s1.skewness_pop(); float32(got) != 0.106098293 {
+		t.Errorf("got %v, want 0.1061", got)
+	}
+	if got := s1.skewness_samp(); float32(got) != 0.1258171 {
+		t.Errorf("got %v, want 0.1258", got)
+	}
+	if got := s1.raw_kurtosis_pop(); float32(got) != 2.3121266 {
+		t.Errorf("got %v, want 2.3121", got)
+	}
+	if got := s1.raw_kurtosis_samp(); float32(got) != 2.7482237 {
+		t.Errorf("got %v, want 2.7483", got)
+	}
+
+	var s2 welford
+
+	s2.enqueue(+0.5377)
+	s2.enqueue(+1.8339)
+	s2.enqueue(-2.2588)
+	s2.enqueue(+0.8622)
+	s2.enqueue(+0.3188)
+	s2.enqueue(-1.3077)
+	s2.enqueue(-0.4336)
+	s2.enqueue(+0.3426)
+	s2.enqueue(+3.5784)
+	s2.enqueue(+2.7694)
+
+	if got, want := s1.mean(), s2.mean(); got != want {
+		t.Errorf("got %v, want %v", got, want)
+	}
+	if got, want := s1.stddev_pop(), s2.stddev_pop(); got != want {
+		t.Errorf("got %v, want %v", got, want)
+	}
+	if got, want := s1.stddev_samp(), s2.stddev_samp(); got != want {
+		t.Errorf("got %v, want %v", got, want)
+	}
+
+	s1.enqueue(math.Pi)
+	s1.enqueue(math.Sqrt2)
+	s1.enqueue(math.E)
+	s1.dequeue(math.Pi)
+	s1.dequeue(math.E)
+	s1.dequeue(math.Sqrt2)
+
+	if got := s1.skewness_pop(); float32(got) != 0.106098293 {
+		t.Errorf("got %v, want 0.1061", got)
+	}
+	if got := s1.skewness_samp(); float32(got) != 0.1258171 {
+		t.Errorf("got %v, want 0.1258", got)
+	}
+	if got := s1.raw_kurtosis_pop(); float32(got) != 2.3121266 {
+		t.Errorf("got %v, want 2.3121", got)
+	}
+	if got := s1.raw_kurtosis_samp(); float32(got) != 2.7482237 {
+		t.Errorf("got %v, want 2.7483", got)
+	}
+}

ext/stats/percentile.go

@@ -11,8 +11,12 @@ import (
 	"github.com/ncruces/sort/quick"
 )
 
+// Compatible with:
+// https://sqlite.org/src/file/ext/misc/percentile.c
+
 const (
 	median = iota
+	percentile_100
 	percentile_cont
 	percentile_disc
 )
@@ -28,17 +32,25 @@ type percentile struct {
 }
 
 func (q *percentile) Step(ctx sqlite3.Context, arg ...sqlite3.Value) {
-	if a := arg[0]; a.NumericType() != sqlite3.NULL {
-		q.nums = append(q.nums, a.Float())
+	a := arg[0]
+	f := a.Float()
+	if f != 0.0 || a.NumericType() != sqlite3.NULL {
+		q.nums = append(q.nums, f)
 	}
-	if q.kind != median {
-		q.arg1 = arg[1].Blob(q.arg1[:0])
+	if q.kind != median && q.arg1 == nil {
+		q.arg1 = append(q.arg1, arg[1].RawText()...)
 	}
 }
 
 func (q *percentile) Inverse(ctx sqlite3.Context, arg ...sqlite3.Value) {
-	// Implementing inverse allows certain queries that don't really need it to succeed.
-	ctx.ResultError(util.ErrorString("percentile: may not be used as a window function"))
+	a := arg[0]
+	f := a.Float()
+	if f != 0.0 || a.NumericType() != sqlite3.NULL {
+		i := slices.Index(q.nums, f)
+		l := len(q.nums) - 1
+		q.nums[i] = q.nums[l]
+		q.nums = q.nums[:l]
+	}
 }
 
 func (q *percentile) Value(ctx sqlite3.Context) {
@@ -52,39 +64,42 @@ func (q *percentile) Value(ctx sqlite3.Context) {
 		floats []float64
 	)
 	if q.kind == median {
-		float, err = getPercentile(q.nums, 0.5, false)
+		float, err = q.at(0.5)
 		ctx.ResultFloat(float)
 	} else if err = json.Unmarshal(q.arg1, &float); err == nil {
-		float, err = getPercentile(q.nums, float, q.kind == percentile_disc)
+		float, err = q.at(float)
 		ctx.ResultFloat(float)
 	} else if err = json.Unmarshal(q.arg1, &floats); err == nil {
-		err = getPercentiles(q.nums, floats, q.kind == percentile_disc)
+		err = q.atMore(floats)
 		ctx.ResultJSON(floats)
 	}
 	if err != nil {
-		ctx.ResultError(fmt.Errorf("percentile: %w", err))
+		ctx.ResultError(fmt.Errorf("percentile: %w", err)) // notest
 	}
 }
 
-func getPercentile(nums []float64, pos float64, disc bool) (float64, error) {
+func (q *percentile) at(pos float64) (float64, error) {
+	if q.kind == percentile_100 {
+		pos = pos / 100
+	}
 	if pos < 0 || pos > 1 {
 		return 0, util.ErrorString("invalid pos")
 	}
 
-	i, f := math.Modf(pos * float64(len(nums)-1))
-	m0 := quick.Select(nums, int(i))
+	i, f := math.Modf(pos * float64(len(q.nums)-1))
+	m0 := quick.Select(q.nums, int(i))
 
-	if f == 0 || disc {
+	if f == 0 || q.kind == percentile_disc {
 		return m0, nil
 	}
 
-	m1 := slices.Min(nums[int(i)+1:])
-	return math.FMA(f, m1, -math.FMA(f, m0, -m0)), nil
+	m1 := slices.Min(q.nums[int(i)+1:])
+	return util.Lerp(m0, m1, f), nil
 }
 
-func getPercentiles(nums []float64, pos []float64, disc bool) error {
+func (q *percentile) atMore(pos []float64) error {
 	for i := range pos {
-		v, err := getPercentile(nums, pos[i], disc)
+		v, err := q.at(pos[i])
 		if err != nil {
 			return err
 		}

ext/stats/percentile_test.go

@@ -6,7 +6,6 @@ import (
 
 	"github.com/ncruces/go-sqlite3"
 	_ "github.com/ncruces/go-sqlite3/embed"
-	"github.com/ncruces/go-sqlite3/ext/stats"
 	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
 )
 
@@ -19,8 +18,6 @@ func TestRegister_percentile(t *testing.T) {
 	}
 	defer db.Close()
 
-	stats.Register(db)
-
 	err = db.Exec(`CREATE TABLE data (x)`)
 	if err != nil {
 		t.Fatal(err)
@@ -34,6 +31,7 @@ func TestRegister_percentile(t *testing.T) {
 	stmt, _, err := db.Prepare(`
 		SELECT
 			median(x),
+			percentile(x, 50),
 			percentile_disc(x, 0.5),
 			percentile_cont(x, '[0.25, 0.5, 0.75]')
 		FROM data`)
@@ -44,11 +42,14 @@ func TestRegister_percentile(t *testing.T) {
 		if got := stmt.ColumnFloat(0); got != 10 {
 			t.Errorf("got %v, want 10", got)
 		}
-		if got := stmt.ColumnFloat(1); got != 7 {
+		if got := stmt.ColumnFloat(1); got != 10 {
+			t.Errorf("got %v, want 10", got)
+		}
+		if got := stmt.ColumnFloat(2); got != 7 {
 			t.Errorf("got %v, want 7", got)
 		}
 		var got []float64
-		if err := stmt.ColumnJSON(2, &got); err != nil {
+		if err := stmt.ColumnJSON(3, &got); err != nil {
 			t.Error(err)
 		}
 		if !slices.Equal(got, []float64{6.25, 10, 13.75}) {
@@ -57,9 +58,44 @@ func TestRegister_percentile(t *testing.T) {
 	}
 	stmt.Close()
 
+	stmt, _, err = db.Prepare(`
+		SELECT
+			median(x) OVER (ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
+		FROM data`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if stmt.Step() {
+		if got := stmt.ColumnFloat(0); got != 5.5 {
+			t.Errorf("got %v, want 5.5", got)
+		}
+	}
+	if stmt.Step() {
+		if got := stmt.ColumnFloat(0); got != 7 {
+			t.Errorf("got %v, want 7", got)
+		}
+	}
+	if stmt.Step() {
+		if got := stmt.ColumnFloat(0); got != 10 {
+			t.Errorf("got %v, want 10", got)
+		}
+	}
+	if stmt.Step() {
+		if got := stmt.ColumnFloat(0); got != 14.5 {
+			t.Errorf("got %v, want 14.5", got)
+		}
+	}
+	if stmt.Step() {
+		if got := stmt.ColumnFloat(0); got != 16 {
+			t.Errorf("got %v, want 16", got)
+		}
+	}
+	stmt.Close()
+
 	stmt, _, err = db.Prepare(`
 		SELECT
 			median(x),
+			percentile(x, 50),
 			percentile_disc(x, 0.5),
 			percentile_cont(x, '[0.25, 0.5, 0.75]')
 		FROM data
@@ -74,8 +110,11 @@ func TestRegister_percentile(t *testing.T) {
 		if got := stmt.ColumnFloat(1); got != 4 {
 			t.Errorf("got %v, want 4", got)
 		}
+		if got := stmt.ColumnFloat(2); got != 4 {
+			t.Errorf("got %v, want 4", got)
+		}
 		var got []float64
-		if err := stmt.ColumnJSON(2, &got); err != nil {
+		if err := stmt.ColumnJSON(3, &got); err != nil {
 			t.Error(err)
 		}
 		if !slices.Equal(got, []float64{4, 4, 4}) {
@@ -87,6 +126,7 @@ func TestRegister_percentile(t *testing.T) {
 	stmt, _, err = db.Prepare(`
 		SELECT
 			median(x),
+			percentile(x, 50),
 			percentile_disc(x, 0.5),
 			percentile_cont(x, '[0.25, 0.5, 0.75]')
 		FROM data
@@ -104,6 +144,9 @@ func TestRegister_percentile(t *testing.T) {
 		if got := stmt.ColumnType(2); got != sqlite3.NULL {
 			t.Error("want NULL")
 		}
+		if got := stmt.ColumnType(3); got != sqlite3.NULL {
+			t.Error("want NULL")
+		}
 	}
 	stmt.Close()
 

ext/stats/stats.go

@@ -1,13 +1,17 @@
 // Package stats provides aggregate functions for statistics.
 //
 // Provided functions:
-//   - stddev_pop: population standard deviation
-//   - stddev_samp: sample standard deviation
 //   - var_pop: population variance
 //   - var_samp: sample variance
+//   - stddev_pop: population standard deviation
+//   - stddev_samp: sample standard deviation
+//   - skewness_pop: Pearson population skewness
+//   - skewness_samp: Pearson sample skewness
+//   - kurtosis_pop: Fisher population excess kurtosis
+//   - kurtosis_samp: Fisher sample excess kurtosis
 //   - covar_pop: population covariance
 //   - covar_samp: sample covariance
-//   - corr: correlation coefficient
+//   - corr: Pearson correlation coefficient
 //   - regr_r2: correlation coefficient squared
 //   - regr_avgx: average of the independent variable
 //   - regr_avgy: average of the dependent variable
@@ -17,10 +21,12 @@
 //   - regr_count: count non-null pairs of variables
 //   - regr_slope: slope of the least-squares-fit linear equation
 //   - regr_intercept: y-intercept of the least-squares-fit linear equation
-//   - regr_json: all regr stats in a JSON object
-//   - percentile_disc: discrete percentile
-//   - percentile_cont: continuous percentile
-//   - median: median value
+//   - regr_json: all regr stats as a JSON object
+//   - percentile_disc: discrete quantile
+//   - percentile_cont: continuous quantile
+//   - percentile: continuous percentile
+//   - median: middle value
+//   - mode: most frequent value
 //   - every: boolean and
 //   - some: boolean or
 //
@@ -44,33 +50,45 @@
 // [ANSI SQL Aggregate Functions]: https://www.oreilly.com/library/view/sql-in-a/9780596155322/ch04s02.html
 package stats
 
-import "github.com/ncruces/go-sqlite3"
+import (
+	"errors"
+
+	"github.com/ncruces/go-sqlite3"
+)
 
 // Register registers statistics functions.
-func Register(db *sqlite3.Conn) {
-	flags := sqlite3.DETERMINISTIC | sqlite3.INNOCUOUS
-	db.CreateWindowFunction("var_pop", 1, flags, newVariance(var_pop))
-	db.CreateWindowFunction("var_samp", 1, flags, newVariance(var_samp))
-	db.CreateWindowFunction("stddev_pop", 1, flags, newVariance(stddev_pop))
-	db.CreateWindowFunction("stddev_samp", 1, flags, newVariance(stddev_samp))
-	db.CreateWindowFunction("covar_pop", 2, flags, newCovariance(var_pop))
-	db.CreateWindowFunction("covar_samp", 2, flags, newCovariance(var_samp))
-	db.CreateWindowFunction("corr", 2, flags, newCovariance(corr))
-	db.CreateWindowFunction("regr_r2", 2, flags, newCovariance(regr_r2))
-	db.CreateWindowFunction("regr_sxx", 2, flags, newCovariance(regr_sxx))
-	db.CreateWindowFunction("regr_syy", 2, flags, newCovariance(regr_syy))
-	db.CreateWindowFunction("regr_sxy", 2, flags, newCovariance(regr_sxy))
-	db.CreateWindowFunction("regr_avgx", 2, flags, newCovariance(regr_avgx))
-	db.CreateWindowFunction("regr_avgy", 2, flags, newCovariance(regr_avgy))
-	db.CreateWindowFunction("regr_slope", 2, flags, newCovariance(regr_slope))
-	db.CreateWindowFunction("regr_intercept", 2, flags, newCovariance(regr_intercept))
-	db.CreateWindowFunction("regr_count", 2, flags, newCovariance(regr_count))
-	db.CreateWindowFunction("regr_json", 2, flags, newCovariance(regr_json))
-	db.CreateWindowFunction("median", 1, flags, newPercentile(median))
-	db.CreateWindowFunction("percentile_cont", 2, flags, newPercentile(percentile_cont))
-	db.CreateWindowFunction("percentile_disc", 2, flags, newPercentile(percentile_disc))
-	db.CreateWindowFunction("every", 1, flags, newBoolean(every))
-	db.CreateWindowFunction("some", 1, flags, newBoolean(some))
+func Register(db *sqlite3.Conn) error {
+	const flags = sqlite3.DETERMINISTIC | sqlite3.INNOCUOUS
+	const order = sqlite3.SELFORDER1 | flags
+	return errors.Join(
+		db.CreateWindowFunction("var_pop", 1, flags, newVariance(var_pop)),
+		db.CreateWindowFunction("var_samp", 1, flags, newVariance(var_samp)),
+		db.CreateWindowFunction("stddev_pop", 1, flags, newVariance(stddev_pop)),
+		db.CreateWindowFunction("stddev_samp", 1, flags, newVariance(stddev_samp)),
+		db.CreateWindowFunction("skewness_pop", 1, flags, newMoments(skewness_pop)),
+		db.CreateWindowFunction("skewness_samp", 1, flags, newMoments(skewness_samp)),
+		db.CreateWindowFunction("kurtosis_pop", 1, flags, newMoments(kurtosis_pop)),
+		db.CreateWindowFunction("kurtosis_samp", 1, flags, newMoments(kurtosis_samp)),
+		db.CreateWindowFunction("covar_pop", 2, flags, newCovariance(var_pop)),
+		db.CreateWindowFunction("covar_samp", 2, flags, newCovariance(var_samp)),
+		db.CreateWindowFunction("corr", 2, flags, newCovariance(corr)),
+		db.CreateWindowFunction("regr_r2", 2, flags, newCovariance(regr_r2)),
+		db.CreateWindowFunction("regr_sxx", 2, flags, newCovariance(regr_sxx)),
+		db.CreateWindowFunction("regr_syy", 2, flags, newCovariance(regr_syy)),
+		db.CreateWindowFunction("regr_sxy", 2, flags, newCovariance(regr_sxy)),
+		db.CreateWindowFunction("regr_avgx", 2, flags, newCovariance(regr_avgx)),
+		db.CreateWindowFunction("regr_avgy", 2, flags, newCovariance(regr_avgy)),
+		db.CreateWindowFunction("regr_slope", 2, flags, newCovariance(regr_slope)),
+		db.CreateWindowFunction("regr_intercept", 2, flags, newCovariance(regr_intercept)),
+		db.CreateWindowFunction("regr_count", 2, flags, newCovariance(regr_count)),
+		db.CreateWindowFunction("regr_json", 2, flags, newCovariance(regr_json)),
+		db.CreateWindowFunction("median", 1, order, newPercentile(median)),
+		db.CreateWindowFunction("percentile", 2, order, newPercentile(percentile_100)),
+		db.CreateWindowFunction("percentile_cont", 2, order, newPercentile(percentile_cont)),
+		db.CreateWindowFunction("percentile_disc", 2, order, newPercentile(percentile_disc)),
+		db.CreateWindowFunction("every", 1, flags, newBoolean(every)),
+		db.CreateWindowFunction("some", 1, flags, newBoolean(some)),
+		db.CreateWindowFunction("mode", 1, order, newMode))
 }
 
 const (
@@ -78,6 +96,10 @@ const (
 	var_samp
 	stddev_pop
 	stddev_samp
+	skewness_pop
+	skewness_samp
+	kurtosis_pop
+	kurtosis_samp
 	corr
 	regr_r2
 	regr_sxx
@@ -91,6 +113,23 @@ const (
 	regr_json
 )
 
+func special(kind int, n int64) (null, zero bool) {
+	switch kind {
+	case var_pop, stddev_pop, regr_sxx, regr_syy, regr_sxy:
+		return n <= 0, n == 1
+	case regr_avgx, regr_avgy:
+		return n <= 0, false
+	case kurtosis_samp:
+		return n <= 3, false
+	case skewness_samp:
+		return n <= 2, false
+	case skewness_pop:
+		return n <= 1, n == 2
+	default:
+		return n <= 1, false
+	}
+}
+
 func newVariance(kind int) func() sqlite3.AggregateFunction {
 	return func() sqlite3.AggregateFunction { return &variance{kind: kind} }
 }
@@ -101,6 +140,14 @@ type variance struct {
 }
 
 func (fn *variance) Value(ctx sqlite3.Context) {
+	switch null, zero := special(fn.kind, fn.n); {
+	case zero:
+		ctx.ResultFloat(0)
+		return
+	case null:
+		return
+	}
+
 	var r float64
 	switch fn.kind {
 	case var_pop:
@@ -116,14 +163,18 @@ func (fn *variance) Value(ctx sqlite3.Context) {
 }
 
 func (fn *variance) Step(ctx sqlite3.Context, arg ...sqlite3.Value) {
-	if a := arg[0]; a.NumericType() != sqlite3.NULL {
-		fn.enqueue(a.Float())
+	a := arg[0]
+	f := a.Float()
+	if f != 0.0 || a.NumericType() != sqlite3.NULL {
+		fn.enqueue(f)
 	}
 }
 
 func (fn *variance) Inverse(ctx sqlite3.Context, arg ...sqlite3.Value) {
-	if a := arg[0]; a.NumericType() != sqlite3.NULL {
-		fn.dequeue(a.Float())
+	a := arg[0]
+	f := a.Float()
+	if f != 0.0 || a.NumericType() != sqlite3.NULL {
+		fn.dequeue(f)
 	}
 }
 
@@ -137,6 +188,18 @@ type covariance struct {
 }
 
 func (fn *covariance) Value(ctx sqlite3.Context) {
+	if fn.kind == regr_count {
+		ctx.ResultInt64(fn.regr_count())
+		return
+	}
+	switch null, zero := special(fn.kind, fn.n); {
+	case zero:
+		ctx.ResultFloat(0)
+		return
+	case null:
+		return
+	}
+
 	var r float64
 	switch fn.kind {
 	case var_pop:
@@ -161,26 +224,80 @@ func (fn *covariance) Value(ctx sqlite3.Context) {
 		r = fn.regr_slope()
 	case regr_intercept:
 		r = fn.regr_intercept()
-	case regr_count:
-		ctx.ResultInt64(fn.regr_count())
-		return
 	case regr_json:
-		ctx.ResultText(fn.regr_json())
+		var buf [128]byte
+		ctx.ResultRawText(fn.regr_json(buf[:0]))
 		return
 	}
 	ctx.ResultFloat(r)
 }
 
 func (fn *covariance) Step(ctx sqlite3.Context, arg ...sqlite3.Value) {
-	a, b := arg[0], arg[1]
-	if a.NumericType() != sqlite3.NULL && b.NumericType() != sqlite3.NULL {
-		fn.enqueue(a.Float(), b.Float())
+	b, a := arg[1], arg[0] // avoid a bounds check
+	fa := a.Float()
+	fb := b.Float()
+	if true &&
+		(fa != 0.0 || a.NumericType() != sqlite3.NULL) &&
+		(fb != 0.0 || b.NumericType() != sqlite3.NULL) {
+		fn.enqueue(fa, fb)
 	}
 }
 
 func (fn *covariance) Inverse(ctx sqlite3.Context, arg ...sqlite3.Value) {
-	a, b := arg[0], arg[1]
-	if a.NumericType() != sqlite3.NULL && b.NumericType() != sqlite3.NULL {
-		fn.dequeue(a.Float(), b.Float())
+	b, a := arg[1], arg[0] // avoid a bounds check
+	fa := a.Float()
+	fb := b.Float()
+	if true &&
+		(fa != 0.0 || a.NumericType() != sqlite3.NULL) &&
+		(fb != 0.0 || b.NumericType() != sqlite3.NULL) {
+		fn.dequeue(fa, fb)
+	}
+}
+
+func newMoments(kind int) func() sqlite3.AggregateFunction {
+	return func() sqlite3.AggregateFunction { return &momentfn{kind: kind} }
+}
+
+type momentfn struct {
+	kind int
+	moments
+}
+
+func (fn *momentfn) Value(ctx sqlite3.Context) {
+	switch null, zero := special(fn.kind, fn.n); {
+	case zero:
+		ctx.ResultFloat(0)
+		return
+	case null:
+		return
+	}
+
+	var r float64
+	switch fn.kind {
+	case skewness_pop:
+		r = fn.skewness_pop()
+	case skewness_samp:
+		r = fn.skewness_samp()
+	case kurtosis_pop:
+		r = fn.kurtosis_pop()
+	case kurtosis_samp:
+		r = fn.kurtosis_samp()
+	}
+	ctx.ResultFloat(r)
+}
+
+func (fn *momentfn) Step(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	a := arg[0]
+	f := a.Float()
+	if f != 0.0 || a.NumericType() != sqlite3.NULL {
+		fn.enqueue(f)
+	}
+}
+
+func (fn *momentfn) Inverse(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	a := arg[0]
+	f := a.Float()
+	if f != 0.0 || a.NumericType() != sqlite3.NULL {
+		fn.dequeue(f)
 	}
 }

ext/stats/stats_test.go

@@ -10,6 +10,11 @@ import (
 	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
 )
 
+func TestMain(m *testing.M) {
+	sqlite3.AutoExtension(stats.Register)
+	m.Run()
+}
+
 func TestRegister_variance(t *testing.T) {
 	t.Parallel()
 
@@ -19,23 +24,34 @@ func TestRegister_variance(t *testing.T) {
 	}
 	defer db.Close()
 
-	stats.Register(db)
-
 	err = db.Exec(`CREATE TABLE data (x)`)
 	if err != nil {
 		t.Fatal(err)
 	}
 
+	stmt, _, err := db.Prepare(`SELECT stddev_pop(x) FROM data`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if stmt.Step() {
+		if got := stmt.ColumnType(0); got != sqlite3.NULL {
+			t.Errorf("got %v, want NULL", got)
+		}
+	}
+	stmt.Close()
+
 	err = db.Exec(`INSERT INTO data (x) VALUES (4), (7.0), ('13'), (NULL), (16)`)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	stmt, _, err := db.Prepare(`
+	stmt, _, err = db.Prepare(`
 		SELECT
 			sum(x), avg(x),
 			var_samp(x), var_pop(x),
-			stddev_samp(x), stddev_pop(x)
+			stddev_samp(x), stddev_pop(x),
+			skewness_samp(x), skewness_pop(x),
+			kurtosis_samp(x), kurtosis_pop(x)
 		FROM data`)
 	if err != nil {
 		t.Fatal(err)
@@ -59,10 +75,27 @@ func TestRegister_variance(t *testing.T) {
 		if got := stmt.ColumnFloat(5); got != math.Sqrt(22.5) {
 			t.Errorf("got %v, want √22.5", got)
 		}
+		if got := stmt.ColumnFloat(6); got != 0 {
+			t.Errorf("got %v, want zero", got)
+		}
+		if got := stmt.ColumnFloat(7); got != 0 {
+			t.Errorf("got %v, want zero", got)
+		}
+		if got := stmt.ColumnFloat(8); float32(got) != -3.3 {
+			t.Errorf("got %v, want -3.3", got)
+		}
+		if got := stmt.ColumnFloat(9); got != -1.64 {
+			t.Errorf("got %v, want -1.64", got)
+		}
 	}
 	stmt.Close()
 
-	stmt, _, err = db.Prepare(`SELECT var_samp(x) OVER (ROWS 1 PRECEDING) FROM data`)
+	stmt, _, err = db.Prepare(`
+		SELECT
+	 		var_samp(x) OVER (ROWS 1 PRECEDING),
+			var_pop(x)  OVER (ROWS 1 PRECEDING),
+	 		skewness_pop(x) OVER (ROWS 1 PRECEDING)
+		FROM data`)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -88,19 +121,31 @@ func TestRegister_covariance(t *testing.T) {
 	}
 	defer db.Close()
 
-	stats.Register(db)
-
 	err = db.Exec(`CREATE TABLE data (y, x)`)
 	if err != nil {
 		t.Fatal(err)
 	}
 
+	stmt, _, err := db.Prepare(`SELECT regr_count(y, x), regr_json(y, x) FROM data`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if stmt.Step() {
+		if got := stmt.ColumnInt(0); got != 0 {
+			t.Errorf("got %v, want 0", got)
+		}
+		if got := stmt.ColumnType(1); got != sqlite3.NULL {
+			t.Errorf("got %v, want NULL", got)
+		}
+	}
+	stmt.Close()
+
 	err = db.Exec(`INSERT INTO data (y, x) VALUES (3, 70), (5, 80), (2, 60), (7, 90), (4, 75)`)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	stmt, _, err := db.Prepare(`SELECT
+	stmt, _, err = db.Prepare(`SELECT
 		corr(y, x), covar_samp(y, x), covar_pop(y, x),
 		regr_avgy(y, x), regr_avgx(y, x),
 		regr_syy(y, x), regr_sxx(y, x), regr_sxy(y, x),
@@ -156,7 +201,12 @@ func TestRegister_covariance(t *testing.T) {
 	}
 	stmt.Close()
 
-	stmt, _, err = db.Prepare(`SELECT covar_samp(y, x) OVER (ROWS 1 PRECEDING) FROM data`)
+	stmt, _, err = db.Prepare(`
+		SELECT
+	 		covar_samp(y, x) OVER (ROWS 1 PRECEDING),
+	 		covar_pop(y, x)  OVER (ROWS 1 PRECEDING),
+			regr_avgx(y, x)  OVER (ROWS 1 PRECEDING)
+		FROM data`)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -170,6 +220,9 @@ func TestRegister_covariance(t *testing.T) {
 			t.Errorf("got %v, want %v", got, want[i])
 		}
 	}
+	if stmt.Err() != nil {
+		t.Fatal(stmt.Err())
+	}
 	stmt.Close()
 }
 
@@ -217,8 +270,6 @@ func Benchmark_variance(b *testing.B) {
 	}
 	defer db.Close()
 
-	stats.Register(db)
-
 	stmt, _, err := db.Prepare(`SELECT var_pop(value) FROM generate_series(0, ?)`)
 	if err != nil {
 		b.Fatal(err)

ext/stats/welford.go

@@ -3,22 +3,20 @@ package stats
 import (
 	"math"
 	"strconv"
-	"strings"
+
+	"github.com/ncruces/go-sqlite3/internal/util"
 )
 
 // Welford's algorithm with Kahan summation:
+// The effect of truncation in statistical computation [van Reeken, AJ 1970]
 // https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Welford's_online_algorithm
-// https://en.wikipedia.org/wiki/Kahan_summation_algorithm
-
-// See also:
-// https://duckdb.org/docs/sql/aggregates.html#statistical-aggregates
 
 type welford struct {
 	m1, m2 kahan
 	n      int64
 }
 
-func (w welford) average() float64 {
+func (w welford) mean() float64 {
 	return w.m1.hi
 }
 
@@ -39,17 +37,23 @@ func (w welford) stddev_samp() float64 {
 }
 
 func (w *welford) enqueue(x float64) {
-	w.n++
+	n := w.n + 1
+	w.n = n
 	d1 := x - w.m1.hi - w.m1.lo
-	w.m1.add(d1 / float64(w.n))
+	w.m1.add(d1 / float64(n))
 	d2 := x - w.m1.hi - w.m1.lo
 	w.m2.add(d1 * d2)
 }
 
 func (w *welford) dequeue(x float64) {
-	w.n--
+	n := w.n - 1
+	if n <= 0 {
+		*w = welford{}
+		return
+	}
+	w.n = n
 	d1 := x - w.m1.hi - w.m1.lo
-	w.m1.sub(d1 / float64(w.n))
+	w.m1.sub(d1 / float64(n))
 	d2 := x - w.m1.hi - w.m1.lo
 	w.m2.sub(d1 * d2)
 }
@@ -112,38 +116,35 @@ func (w welford2) regr_r2() float64 {
 	return w.cov.hi * w.cov.hi / (w.m2y.hi * w.m2x.hi)
 }
 
-func (w welford2) regr_json() string {
-	var json strings.Builder
-	var num [32]byte
-	json.Grow(128)
-	json.WriteString(`{"count":`)
-	json.Write(strconv.AppendInt(num[:0], w.regr_count(), 10))
-	json.WriteString(`,"avgy":`)
-	json.Write(strconv.AppendFloat(num[:0], w.regr_avgy(), 'g', -1, 64))
-	json.WriteString(`,"avgx":`)
-	json.Write(strconv.AppendFloat(num[:0], w.regr_avgx(), 'g', -1, 64))
-	json.WriteString(`,"syy":`)
-	json.Write(strconv.AppendFloat(num[:0], w.regr_syy(), 'g', -1, 64))
-	json.WriteString(`,"sxx":`)
-	json.Write(strconv.AppendFloat(num[:0], w.regr_sxx(), 'g', -1, 64))
-	json.WriteString(`,"sxy":`)
-	json.Write(strconv.AppendFloat(num[:0], w.regr_sxy(), 'g', -1, 64))
-	json.WriteString(`,"slope":`)
-	json.Write(strconv.AppendFloat(num[:0], w.regr_slope(), 'g', -1, 64))
-	json.WriteString(`,"intercept":`)
-	json.Write(strconv.AppendFloat(num[:0], w.regr_intercept(), 'g', -1, 64))
-	json.WriteString(`,"r2":`)
-	json.Write(strconv.AppendFloat(num[:0], w.regr_r2(), 'g', -1, 64))
-	json.WriteByte('}')
-	return json.String()
+func (w welford2) regr_json(dst []byte) []byte {
+	dst = append(dst, `{"count":`...)
+	dst = strconv.AppendInt(dst, w.regr_count(), 10)
+	dst = append(dst, `,"avgy":`...)
+	dst = util.AppendNumber(dst, w.regr_avgy())
+	dst = append(dst, `,"avgx":`...)
+	dst = util.AppendNumber(dst, w.regr_avgx())
+	dst = append(dst, `,"syy":`...)
+	dst = util.AppendNumber(dst, w.regr_syy())
+	dst = append(dst, `,"sxx":`...)
+	dst = util.AppendNumber(dst, w.regr_sxx())
+	dst = append(dst, `,"sxy":`...)
+	dst = util.AppendNumber(dst, w.regr_sxy())
+	dst = append(dst, `,"slope":`...)
+	dst = util.AppendNumber(dst, w.regr_slope())
+	dst = append(dst, `,"intercept":`...)
+	dst = util.AppendNumber(dst, w.regr_intercept())
+	dst = append(dst, `,"r2":`...)
+	dst = util.AppendNumber(dst, w.regr_r2())
+	return append(dst, '}')
 }
 
 func (w *welford2) enqueue(y, x float64) {
-	w.n++
+	n := w.n + 1
+	w.n = n
 	d1y := y - w.m1y.hi - w.m1y.lo
 	d1x := x - w.m1x.hi - w.m1x.lo
-	w.m1y.add(d1y / float64(w.n))
-	w.m1x.add(d1x / float64(w.n))
+	w.m1y.add(d1y / float64(n))
+	w.m1x.add(d1x / float64(n))
 	d2y := y - w.m1y.hi - w.m1y.lo
 	d2x := x - w.m1x.hi - w.m1x.lo
 	w.m2y.add(d1y * d2y)
@@ -152,30 +153,19 @@ func (w *welford2) enqueue(y, x float64) {
 }
 
 func (w *welford2) dequeue(y, x float64) {
-	w.n--
+	n := w.n - 1
+	if n <= 0 {
+		*w = welford2{}
+		return
+	}
+	w.n = n
 	d1y := y - w.m1y.hi - w.m1y.lo
 	d1x := x - w.m1x.hi - w.m1x.lo
-	w.m1y.sub(d1y / float64(w.n))
-	w.m1x.sub(d1x / float64(w.n))
+	w.m1y.sub(d1y / float64(n))
+	w.m1x.sub(d1x / float64(n))
 	d2y := y - w.m1y.hi - w.m1y.lo
 	d2x := x - w.m1x.hi - w.m1x.lo
 	w.m2y.sub(d1y * d2y)
 	w.m2x.sub(d1x * d2x)
 	w.cov.sub(d1y * d2x)
 }
-
-type kahan struct{ hi, lo float64 }
-
-func (k *kahan) add(x float64) {
-	y := k.lo + x
-	t := k.hi + y
-	k.lo = y - (t - k.hi)
-	k.hi = t
-}
-
-func (k *kahan) sub(x float64) {
-	y := k.lo - x
-	t := k.hi + y
-	k.lo = y - (t - k.hi)
-	k.hi = t
-}

ext/stats/welford_test.go

@@ -9,12 +9,14 @@ func Test_welford(t *testing.T) {
 	t.Parallel()
 
 	var s1, s2 welford
+	s1.enqueue(1)
+	s1.dequeue(1)
 
 	s1.enqueue(4)
 	s1.enqueue(7)
 	s1.enqueue(13)
 	s1.enqueue(16)
-	if got := s1.average(); got != 10 {
+	if got := s1.mean(); got != 10 {
 		t.Errorf("got %v, want 10", got)
 	}
 	if got := s1.var_samp(); got != 30 {
@@ -43,6 +45,8 @@ func Test_covar(t *testing.T) {
 	t.Parallel()
 
 	var c1, c2 welford2
+	c1.enqueue(1, 1)
+	c1.dequeue(1, 1)
 
 	c1.enqueue(3, 70)
 	c1.enqueue(5, 80)

ext/unicode/unicode.go

@@ -11,6 +11,12 @@
 //   - the REGEXP operator uses Go [regexp/syntax];
 //   - collation sequences use [collate].
 //
+// It also provides (approximately) from PostgreSQL:
+//   - casefold(),
+//   - initcap(),
+//   - normalize(),
+//   - unaccent().
+//
 // Expect subtle differences (e.g.) in the handling of Turkish case folding.
 //
 // [ICU extension]: https://sqlite.org/src/dir/ext/icu
@@ -18,41 +24,63 @@ package unicode
 
 import (
 	"bytes"
+	"errors"
 	"regexp"
 	"strings"
+	"unicode"
 	"unicode/utf8"
 
-	"github.com/ncruces/go-sqlite3"
-	"github.com/ncruces/go-sqlite3/internal/util"
 	"golang.org/x/text/cases"
 	"golang.org/x/text/collate"
 	"golang.org/x/text/language"
+	"golang.org/x/text/runes"
+	"golang.org/x/text/transform"
+	"golang.org/x/text/unicode/norm"
+
+	"github.com/ncruces/go-sqlite3"
+	"github.com/ncruces/go-sqlite3/internal/util"
 )
 
+// Set RegisterLike to false to not register a Unicode aware LIKE operator.
+// Overriding the built-in LIKE operator disables the [LIKE optimization].
+//
+// [LIKE optimization]: https://sqlite.org/optoverview.html#the_like_optimization
+var RegisterLike = true
+
 // Register registers Unicode aware functions for a database connection.
-func Register(db *sqlite3.Conn) {
-	flags := sqlite3.DETERMINISTIC | sqlite3.INNOCUOUS
+func Register(db *sqlite3.Conn) error {
+	const flags = sqlite3.DETERMINISTIC | sqlite3.INNOCUOUS
+	var lkfn sqlite3.ScalarFunction
+	if RegisterLike {
+		lkfn = like
+	}
+	return errors.Join(
+		db.CreateFunction("like", 2, flags, lkfn),
+		db.CreateFunction("like", 3, flags, lkfn),
+		db.CreateFunction("upper", 1, flags, upper),
+		db.CreateFunction("upper", 2, flags, upper),
+		db.CreateFunction("lower", 1, flags, lower),
+		db.CreateFunction("lower", 2, flags, lower),
+		db.CreateFunction("regexp", 2, flags, regex),
+		db.CreateFunction("initcap", 1, flags, initcap),
+		db.CreateFunction("initcap", 2, flags, initcap),
+		db.CreateFunction("casefold", 1, flags, casefold),
+		db.CreateFunction("unaccent", 1, flags, unaccent),
+		db.CreateFunction("normalize", 1, flags, normalize),
+		db.CreateFunction("normalize", 2, flags, normalize),
+		db.CreateFunction("icu_load_collation", 2, sqlite3.DIRECTONLY,
+			func(ctx sqlite3.Context, arg ...sqlite3.Value) {
+				name := arg[1].Text()
+				if name == "" {
+					return
+				}
 
-	db.CreateFunction("like", 2, flags, like)
-	db.CreateFunction("like", 3, flags, like)
-	db.CreateFunction("upper", 1, flags, upper)
-	db.CreateFunction("upper", 2, flags, upper)
-	db.CreateFunction("lower", 1, flags, lower)
-	db.CreateFunction("lower", 2, flags, lower)
-	db.CreateFunction("regexp", 2, flags, regex)
-	db.CreateFunction("icu_load_collation", 2, sqlite3.DIRECTONLY,
-		func(ctx sqlite3.Context, arg ...sqlite3.Value) {
-			name := arg[1].Text()
-			if name == "" {
-				return
-			}
-
-			err := RegisterCollation(db, arg[0].Text(), name)
-			if err != nil {
-				ctx.ResultError(err)
-				return
-			}
-		})
+				err := RegisterCollation(ctx.Conn(), arg[0].Text(), name)
+				if err != nil {
+					ctx.ResultError(err)
+					return // notest
+				}
+			}))
 }
 
 // RegisterCollation registers a Unicode collation sequence for a database connection.
@@ -64,6 +92,15 @@ func RegisterCollation(db *sqlite3.Conn, locale, name string) error {
 	return db.CreateCollation(name, collate.New(tag).Compare)
 }
 
+// RegisterCollationsNeeded registers Unicode collation sequences on demand for a database connection.
+func RegisterCollationsNeeded(db *sqlite3.Conn) error {
+	return db.CollationNeeded(func(db *sqlite3.Conn, name string) {
+		if tag, err := language.Parse(name); err == nil {
+			db.CreateCollation(name, collate.New(tag).Compare)
+		}
+	})
+}
+
 func upper(ctx sqlite3.Context, arg ...sqlite3.Value) {
 	if len(arg) == 1 {
 		ctx.ResultRawText(bytes.ToUpper(arg[0].RawText()))
@@ -74,7 +111,7 @@ func upper(ctx sqlite3.Context, arg ...sqlite3.Value) {
 		t, err := language.Parse(arg[1].Text())
 		if err != nil {
 			ctx.ResultError(err)
-			return
+			return // notest
 		}
 		c := cases.Upper(t)
 		ctx.SetAuxData(1, c)
@@ -93,7 +130,7 @@ func lower(ctx sqlite3.Context, arg ...sqlite3.Value) {
 		t, err := language.Parse(arg[1].Text())
 		if err != nil {
 			ctx.ResultError(err)
-			return
+			return // notest
 		}
 		c := cases.Lower(t)
 		ctx.SetAuxData(1, c)
@@ -102,16 +139,74 @@ func lower(ctx sqlite3.Context, arg ...sqlite3.Value) {
 	ctx.ResultRawText(cs.Bytes(arg[0].RawText()))
 }
 
+func initcap(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	if len(arg) == 1 {
+		ctx.ResultRawText(bytes.Title(arg[0].RawText()))
+		return
+	}
+	cs, ok := ctx.GetAuxData(1).(cases.Caser)
+	if !ok {
+		t, err := language.Parse(arg[1].Text())
+		if err != nil {
+			ctx.ResultError(err)
+			return // notest
+		}
+		c := cases.Title(t)
+		ctx.SetAuxData(1, c)
+		cs = c
+	}
+	ctx.ResultRawText(cs.Bytes(arg[0].RawText()))
+}
+
+func casefold(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	ctx.ResultRawText(cases.Fold().Bytes(arg[0].RawText()))
+}
+
+func unaccent(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	unaccent := transform.Chain(norm.NFD, runes.Remove(runes.In(unicode.Mn)), norm.NFC)
+	res, _, err := transform.Bytes(unaccent, arg[0].RawText())
+	if err != nil {
+		ctx.ResultError(err) // notest
+	} else {
+		ctx.ResultRawText(res)
+	}
+}
+
+func normalize(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	form := norm.NFC
+	if len(arg) > 1 {
+		switch strings.ToUpper(arg[1].Text()) {
+		case "NFC":
+			//
+		case "NFD":
+			form = norm.NFD
+		case "NFKC":
+			form = norm.NFKC
+		case "NFKD":
+			form = norm.NFKD
+		default:
+			ctx.ResultError(util.ErrorString("unicode: invalid form"))
+			return
+		}
+	}
+	res, _, err := transform.Bytes(form, arg[0].RawText())
+	if err != nil {
+		ctx.ResultError(err) // notest
+	} else {
+		ctx.ResultRawText(res)
+	}
+}
+
 func regex(ctx sqlite3.Context, arg ...sqlite3.Value) {
 	re, ok := ctx.GetAuxData(0).(*regexp.Regexp)
 	if !ok {
 		r, err := regexp.Compile(arg[0].Text())
 		if err != nil {
 			ctx.ResultError(err)
-			return
+			return // notest
 		}
 		re = r
-		ctx.SetAuxData(0, re)
+		ctx.SetAuxData(0, r)
 	}
 	ctx.ResultBool(re.Match(arg[1].RawText()))
 }
@@ -127,6 +222,7 @@ func like(ctx sqlite3.Context, arg ...sqlite3.Value) {
 			return
 		}
 	}
+	_ = arg[1] // bounds check
 
 	type likeData struct {
 		*regexp.Regexp

ext/unicode/unicode_test.go

@@ -2,7 +2,7 @@ package unicode
 
 import (
 	"errors"
-	"reflect"
+	"slices"
 	"testing"
 
 	"github.com/ncruces/go-sqlite3"
@@ -47,6 +47,15 @@ func TestRegister(t *testing.T) {
 		{`upper('istanbul', 'tr-TR')`, "İSTANBUL"},
 		{`lower('Dünyanın İlk Borsası', 'tr-TR')`, "dünyanın ilk borsası"},
 		{`upper('Dünyanın İlk Borsası', 'tr-TR')`, "DÜNYANIN İLK BORSASI"},
+		{`initcap('Kad je hladno Marko nosi džemper')`, "Kad Je Hladno Marko Nosi Džemper"},
+		{`initcap('Kad je hladno Marko nosi džemper', 'hr-HR')`, "Kad Je Hladno Marko Nosi Džemper"},
+		{`normalize(X'61cc88')`, "ä"},
+		{`normalize(X'61cc88', 'NFC' )`, "ä"},
+		{`normalize(X'61cc88', 'NFKC')`, "ä"},
+		{`normalize('ä', 'NFD' )`, "\x61\xcc\x88"},
+		{`normalize('ä', 'NFKD')`, "\x61\xcc\x88"},
+		{`casefold('Maße')`, "masse"},
+		{`unaccent('Hôtel')`, "Hotel"},
 		{`'Hello' REGEXP 'ell'`, "1"},
 		{`'Hello' REGEXP 'el.'`, "1"},
 		{`'Hello' LIKE 'hel_'`, "0"},
@@ -92,7 +101,7 @@ func TestRegister_collation(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.Exec(`SELECT icu_load_collation('fr_FR', 'french')`)
+	err = db.Exec(`SELECT icu_load_collation('fr-FR', 'french')`)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -112,7 +121,58 @@ func TestRegister_collation(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if !reflect.DeepEqual(got, want) {
+	if !slices.Equal(got, want) {
+		t.Error("not equal")
+	}
+
+	err = stmt.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = db.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestRegisterCollationsNeeded(t *testing.T) {
+	t.Parallel()
+
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	RegisterCollationsNeeded(db)
+
+	err = db.Exec(`CREATE TABLE words (word VARCHAR(10))`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = db.Exec(`INSERT INTO words (word) VALUES ('côte'), ('cote'), ('coter'), ('coté'), ('cotée'), ('côté')`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	stmt, _, err := db.Prepare(`SELECT word FROM words ORDER BY word COLLATE fr_FR`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer stmt.Close()
+
+	got, want := []string{}, []string{"cote", "coté", "côte", "côté", "cotée", "coter"}
+
+	for stmt.Step() {
+		got = append(got, stmt.ColumnText(0))
+	}
+	if err := stmt.Err(); err != nil {
+		t.Fatal(err)
+	}
+
+	if !slices.Equal(got, want) {
 		t.Error("not equal")
 	}
 
@@ -154,6 +214,14 @@ func TestRegister_error(t *testing.T) {
 		t.Errorf("got %v, want sqlite3.ERROR", err)
 	}
 
+	err = db.Exec(`SELECT normalize('', 'NF')`)
+	if err == nil {
+		t.Error("want error")
+	}
+	if !errors.Is(err, sqlite3.ERROR) {
+		t.Errorf("got %v, want sqlite3.ERROR", err)
+	}
+
 	err = db.Exec(`SELECT 'hello' REGEXP '\'`)
 	if err == nil {
 		t.Error("want error")

ext/uuid/uuid.go

@@ -0,0 +1,199 @@
+// Package uuid provides functions to generate RFC 4122 UUIDs.
+//
+// https://sqlite.org/src/file/ext/misc/uuid.c
+package uuid
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/google/uuid"
+
+	"github.com/ncruces/go-sqlite3"
+	"github.com/ncruces/go-sqlite3/internal/util"
+)
+
+// Register registers the SQL functions:
+//
+//	uuid([version], [domain/namespace], [id/data])
+//
+// Generates a UUID as a string.
+//
+//	uuid_str(u)
+//
+// Converts a UUID into a well-formed UUID string.
+//
+//	uuid_blob(u)
+//
+// Converts a UUID into a 16-byte blob.
+func Register(db *sqlite3.Conn) error {
+	const flags = sqlite3.DETERMINISTIC | sqlite3.INNOCUOUS
+	return errors.Join(
+		db.CreateFunction("uuid", 0, sqlite3.INNOCUOUS, generate),
+		db.CreateFunction("uuid", 1, sqlite3.INNOCUOUS, generate),
+		db.CreateFunction("uuid", 2, sqlite3.INNOCUOUS, generate),
+		db.CreateFunction("uuid", 3, sqlite3.INNOCUOUS, generate),
+		db.CreateFunction("uuid_str", 1, flags, toString),
+		db.CreateFunction("uuid_blob", 1, flags, toBlob),
+		db.CreateFunction("uuid_extract_version", 1, flags, version),
+		db.CreateFunction("uuid_extract_timestamp", 1, flags, timestamp))
+}
+
+func generate(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	var (
+		ver int
+		err error
+		u   uuid.UUID
+	)
+
+	if len(arg) > 0 {
+		ver = arg[0].Int()
+	} else {
+		ver = 4
+	}
+
+	switch ver {
+	case 1:
+		u, err = uuid.NewUUID()
+	case 4:
+		u, err = uuid.NewRandom()
+	case 6:
+		u, err = uuid.NewV6()
+	case 7:
+		u, err = uuid.NewV7()
+
+	case 2:
+		var domain uuid.Domain
+		if len(arg) > 1 {
+			domain = uuid.Domain(arg[1].Int64())
+			if domain == 0 {
+				if txt := arg[1].RawText(); len(txt) > 0 {
+					switch txt[0] | 0x20 { // to lower
+					case 'g': // group
+						domain = uuid.Group
+					case 'o': // org
+						domain = uuid.Org
+					}
+				}
+			}
+		}
+		switch {
+		case len(arg) > 2:
+			u, err = uuid.NewDCESecurity(domain, uint32(arg[2].Int64()))
+		case domain == uuid.Person:
+			u, err = uuid.NewDCEPerson()
+		case domain == uuid.Group:
+			u, err = uuid.NewDCEGroup()
+		default:
+			err = util.ErrorString("missing id")
+		}
+
+	case 3, 5:
+		if len(arg) < 2 {
+			err = util.ErrorString("missing data")
+			break
+		}
+		ns, err := fromValue(arg[1])
+		if err != nil {
+			space := arg[1].RawText()
+			switch {
+			case bytes.EqualFold(space, []byte("url")):
+				ns = uuid.NameSpaceURL
+			case bytes.EqualFold(space, []byte("oid")):
+				ns = uuid.NameSpaceOID
+			case bytes.EqualFold(space, []byte("dns")):
+				ns = uuid.NameSpaceDNS
+			case bytes.EqualFold(space, []byte("fqdn")):
+				ns = uuid.NameSpaceDNS
+			case bytes.EqualFold(space, []byte("x500")):
+				ns = uuid.NameSpaceX500
+			default:
+				ctx.ResultError(err)
+				return // notest
+			}
+		}
+		if ver == 3 {
+			u = uuid.NewMD5(ns, arg[2].RawBlob())
+		} else {
+			u = uuid.NewSHA1(ns, arg[2].RawBlob())
+		}
+
+	default:
+		err = fmt.Errorf("invalid version: %d", ver)
+	}
+
+	if err != nil {
+		ctx.ResultError(fmt.Errorf("uuid: %w", err)) // notest
+	} else {
+		ctx.ResultText(u.String())
+	}
+}
+
+func fromValue(arg sqlite3.Value) (u uuid.UUID, err error) {
+	switch t := arg.Type(); t {
+	case sqlite3.TEXT:
+		u, err = uuid.ParseBytes(arg.RawText())
+		if err != nil {
+			err = fmt.Errorf("uuid: %w", err)
+		}
+
+	case sqlite3.BLOB:
+		blob := arg.RawBlob()
+		if len := len(blob); len != 16 {
+			err = fmt.Errorf("uuid: invalid BLOB length: %d", len)
+		} else {
+			copy(u[:], blob)
+		}
+
+	default:
+		err = fmt.Errorf("uuid: invalid type: %v", t)
+	}
+	return u, err
+}
+
+func toBlob(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	u, err := fromValue(arg[0])
+	if err != nil {
+		ctx.ResultError(err) // notest
+	} else {
+		ctx.ResultBlob(u[:])
+	}
+}
+
+func toString(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	u, err := fromValue(arg[0])
+	if err != nil {
+		ctx.ResultError(err) // notest
+	} else {
+		ctx.ResultText(u.String())
+	}
+}
+
+func version(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	u, err := fromValue(arg[0])
+	if err != nil {
+		ctx.ResultError(err)
+		return // notest
+	}
+	if u.Variant() == uuid.RFC4122 {
+		ctx.ResultInt64(int64(u.Version()))
+	}
+}
+
+func timestamp(ctx sqlite3.Context, arg ...sqlite3.Value) {
+	u, err := fromValue(arg[0])
+	if err != nil {
+		ctx.ResultError(err)
+		return // notest
+	}
+	if u.Variant() == uuid.RFC4122 {
+		switch u.Version() {
+		case 1, 2, 6, 7:
+			ctx.ResultTime(
+				time.Unix(u.Time().UnixTime()),
+				sqlite3.TimeFormatDefault)
+		}
+	}
+}

ext/uuid/uuid_test.go

@@ -0,0 +1,211 @@
+package uuid
+
+import (
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+
+	"github.com/ncruces/go-sqlite3/driver"
+	_ "github.com/ncruces/go-sqlite3/embed"
+	_ "github.com/ncruces/go-sqlite3/internal/testcfg"
+	"github.com/ncruces/go-sqlite3/vfs/memdb"
+)
+
+func Test_generate(t *testing.T) {
+	t.Parallel()
+	tmp := memdb.TestDB(t)
+
+	db, err := driver.Open(tmp, Register)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	var u uuid.UUID
+
+	// Version 4, SQLite compatible
+	err = db.QueryRow(`SELECT uuid()`).Scan(&u)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got := u.Version(); got != 4 {
+		t.Errorf("got %d, want 4", got)
+	}
+
+	// Invalid version
+	err = db.QueryRow(`SELECT uuid(8)`).Scan(&u)
+	if err == nil {
+		t.Error("want error")
+	}
+
+	// Custom version, no arguments
+	for _, want := range []uuid.Version{1, 2, 4, 6, 7} {
+		err = db.QueryRow(`SELECT uuid(?)`, want).Scan(&u)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got := u.Version(); got != want {
+			t.Errorf("got %d, want %d", got, want)
+		}
+	}
+
+	// Version 2, custom arguments
+	err = db.QueryRow(`SELECT uuid(2, 4)`).Scan(&u)
+	if err == nil {
+		t.Error("want error")
+	}
+
+	err = db.QueryRow(`SELECT uuid(2, 'group')`).Scan(&u)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got := u.Version(); got != 2 {
+		t.Errorf("got %d, want 2", got)
+	}
+	if got := u.Domain(); got != uuid.Group {
+		t.Errorf("got %d, want 1", got)
+	}
+
+	dce := []struct {
+		out uuid.Domain
+		in  any
+		id  uint32
+	}{
+		{uuid.Person, "user", 42},
+		{uuid.Group, "group", 42},
+		{uuid.Org, "org", 42},
+		{uuid.Person, 0, 42},
+		{uuid.Group, 1, 42},
+		{uuid.Org, 2, 42},
+		{3, 3, 42},
+	}
+	for _, tt := range dce {
+		err = db.QueryRow(`SELECT uuid(2, ?, ?)`, tt.in, tt.id).Scan(&u)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got := u.Version(); got != 2 {
+			t.Errorf("got %d, want 2", got)
+		}
+		if got := u.Domain(); got != tt.out {
+			t.Errorf("got %d, want %d", got, tt.out)
+		}
+		if got := u.ID(); got != tt.id {
+			t.Errorf("got %d, want %d", got, tt.id)
+		}
+	}
+
+	// Versions 3 and 5
+	err = db.QueryRow(`SELECT uuid(3)`).Scan(&u)
+	if err == nil {
+		t.Error("want error")
+	}
+
+	err = db.QueryRow(`SELECT uuid(3, 0, '')`).Scan(&u)
+	if err == nil {
+		t.Error("want error")
+	}
+
+	var tstamp time.Time
+	var version uuid.Version
+	err = db.QueryRow(`
+		SELECT
+			column1,
+			uuid_extract_version(column1),
+			uuid_extract_timestamp(column1)
+		FROM (VALUES (uuid(7)))
+	`).Scan(&u, &version, &tstamp)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got := u.Version(); got != version {
+		t.Errorf("got %d, want %d", got, version)
+	}
+	if got := time.Unix(u.Time().UnixTime()); !got.Equal(tstamp) {
+		t.Errorf("got %v, want %v", got, tstamp)
+	}
+
+	tests := []struct {
+		ver  uuid.Version
+		ns   any
+		data string
+		u    uuid.UUID
+	}{
+		{3, "oid", "2.999", uuid.MustParse("31cb1efa-18c4-3d19-89ba-df6a74ddbd1d")},
+		{3, "dns", "www.example.com", uuid.MustParse("5df41881-3aed-3515-88a7-2f4a814cf09e")},
+		{3, "fqdn", "www.example.com", uuid.MustParse("5df41881-3aed-3515-88a7-2f4a814cf09e")},
+		{3, "url", "https://www.example.com/", uuid.MustParse("7fed185f-0864-319f-875b-a3d5458e30ac")},
+		{3, "x500", "CN=Test User 1, O=Example Organization, ST=California, C=US", uuid.MustParse("addf5e97-9287-3834-abfd-7edcbe7db56f")},
+		{3, "url", "https://www.php.net", uuid.MustParse("3f703955-aaba-3e70-a3cb-baff6aa3b28f")},
+		{5, "url", "https://www.php.net", uuid.MustParse("a8f6ae40-d8a7-58f0-be05-a22f94eca9ec")},
+	}
+	for _, tt := range tests {
+		err = db.QueryRow(`SELECT uuid(?, ?, ?)`, tt.ver, tt.ns, tt.data).Scan(&u)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if u != tt.u {
+			t.Errorf("got %v, want %v", u, tt.u)
+		}
+	}
+}
+
+func Test_convert(t *testing.T) {
+	t.Parallel()
+	tmp := memdb.TestDB(t)
+
+	db, err := driver.Open(tmp, Register)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	var u uuid.UUID
+	tests := []string{
+		"'6ba7b8119dad11d180b400c04fd430c8'",
+		"'6ba7b811-9dad-11d1-80b4-00c04fd430c8'",
+		"'{6ba7b811-9dad-11d1-80b4-00c04fd430c8}'",
+		"X'6ba7b8119dad11d180b400c04fd430c8'",
+	}
+
+	for _, tt := range tests {
+		err = db.QueryRow(`SELECT uuid_str(` + tt + `)`).Scan(&u)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if u != uuid.NameSpaceURL {
+			t.Errorf("got %v, want %v", u, uuid.NameSpaceURL)
+		}
+	}
+
+	for _, tt := range tests {
+		err = db.QueryRow(`SELECT uuid_blob(` + tt + `)`).Scan(&u)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if u != uuid.NameSpaceURL {
+			t.Errorf("got %v, want %v", u, uuid.NameSpaceURL)
+		}
+	}
+
+	err = db.QueryRow(`SELECT uuid_str(X'cafe')`).Scan(&u)
+	if err == nil {
+		t.Fatal("want error")
+	}
+
+	err = db.QueryRow(`SELECT uuid_blob(X'cafe')`).Scan(&u)
+	if err == nil {
+		t.Fatal("want error")
+	}
+
+	err = db.QueryRow(`SELECT uuid_extract_version(X'cafe')`).Scan(&u)
+	if err == nil {
+		t.Fatal("want error")
+	}
+
+	err = db.QueryRow(`SELECT uuid_extract_timestamp(X'cafe')`).Scan(&u)
+	if err == nil {
+		t.Fatal("want error")
+	}
+}

ext/zorder/zorder.go

@@ -4,30 +4,33 @@
 package zorder
 
 import (
+	"errors"
+
 	"github.com/ncruces/go-sqlite3"
 	"github.com/ncruces/go-sqlite3/internal/util"
 )
 
 // Register registers the zorder and unzorder SQL functions.
-func Register(db *sqlite3.Conn) {
-	flags := sqlite3.DETERMINISTIC | sqlite3.INNOCUOUS
-	db.CreateFunction("zorder", -1, flags, zorder)
-	db.CreateFunction("unzorder", 3, flags, unzorder)
+func Register(db *sqlite3.Conn) error {
+	const flags = sqlite3.DETERMINISTIC | sqlite3.INNOCUOUS
+	return errors.Join(
+		db.CreateFunction("zorder", -1, flags, zorder),
+		db.CreateFunction("unzorder", 3, flags, unzorder))
 }
 
 func zorder(ctx sqlite3.Context, arg ...sqlite3.Value) {
 	var x [63]int64
-	for i := range arg {
-		x[i] = arg[i].Int64()
-	}
 	if len(arg) > len(x) {
 		ctx.ResultError(util.ErrorString("zorder: too many parameters"))
 		return
 	}
+	for i := range arg {
+		x[i] = arg[i].Int64()
+	}
 
 	var z int64
 	if len(arg) > 0 {
-		for i := 0; i < 63; i++ {
+		for i := range x {
 			j := i % len(arg)
 			z |= (x[j] & 1) << i
 			x[j] >>= 1
@@ -44,9 +47,9 @@ func zorder(ctx sqlite3.Context, arg ...sqlite3.Value) {
 }
 
 func unzorder(ctx sqlite3.Context, arg ...sqlite3.Value) {
-	z := arg[0].Int64()
-	n := arg[1].Int64()
 	i := arg[2].Int64()
+	n := arg[1].Int64()
+	z := arg[0].Int64()
 
 	var k int
 	var x int64