SQLite 3.51.1.

Lock tweaks.
Remove MinLevel.
2026-01-12 22:19:14 +00:00 · 2025-11-30 10:24:34 +00:00 · 2025-11-29 16:12:29 +00:00 · 2025-11-27 17:29:47 +00:00 · 2025-11-27 16:28:16 +00:00 · 2025-11-26 14:07:44 +00:00
27 changed files with 495 additions and 414 deletions
--- a/embed/README.md
+++ b/embed/README.md
@@ -1,6 +1,6 @@
 # Embeddable Wasm build of SQLite

-This folder includes an embeddable Wasm build of SQLite 3.50.4 for use with
+This folder includes an embeddable Wasm build of SQLite 3.51.1 for use with
 [`github.com/ncruces/go-sqlite3`](https://pkg.go.dev/github.com/ncruces/go-sqlite3).

 The following optional features are compiled in:
--- a/embed/bcw2/bcw2.wasm
+++ b/embed/bcw2/bcw2.wasm
--- a/embed/bcw2/build.sh
+++ b/embed/bcw2/build.sh
@@ -15,9 +15,9 @@ cp "$ROOT"/sqlite3/*.[ch] build/
 cp "$ROOT"/sqlite3/*.patch build/
 cd sqlite/

-# https://sqlite.org/src/info/352b363a5d727047
-curl -#L https://github.com/sqlite/sqlite/archive/dbd613c.tar.gz | tar xz --strip-components=1
-# curl -#L https://sqlite.org/src/tarball/sqlite.tar.gz?r=352b363a5d | tar xz --strip-components=1
+# https://sqlite.org/src/info/f273f6b8245c5dca
+curl -#L https://github.com/sqlite/sqlite/archive/7c126d7.tar.gz | tar xz --strip-components=1
+# curl -#L https://sqlite.org/src/tarball/sqlite.tar.gz?r=f273f6b824 | tar xz --strip-components=1

 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"
--- a/embed/bcw2/go.mod
+++ b/embed/bcw2/go.mod
@@ -2,7 +2,7 @@ module github.com/ncruces/go-sqlite3/embed/bcw2

 go 1.24.0

-require github.com/ncruces/go-sqlite3 v0.30.1
+require github.com/ncruces/go-sqlite3 v0.30.2

 require (
 	github.com/ncruces/julianday v1.0.0 // indirect
--- a/embed/bcw2/go.sum
+++ b/embed/bcw2/go.sum
@@ -1,5 +1,5 @@
-github.com/ncruces/go-sqlite3 v0.30.1 h1:pHC3YsyRdJv4pCMB4MO1Q2BXw/CAa+Hoj7GSaKtVk+g=
-github.com/ncruces/go-sqlite3 v0.30.1/go.mod h1:UVsWrQaq1qkcal5/vT5lOJnZCVlR5rsThKdwidjFsKc=
+github.com/ncruces/go-sqlite3 v0.30.2 h1:1GVbHAkKAOwjJd3JYl8ldrYROudfZUOah7oXPD7VZbQ=
+github.com/ncruces/go-sqlite3 v0.30.2/go.mod h1:AxKu9sRxkludimFocbktlY6LiYSkxiI5gTA8r+os/Nw=
 github.com/ncruces/julianday v1.0.0 h1:fH0OKwa7NWvniGQtxdJRxAgkBMolni2BjDHaWTxqt7M=
 github.com/ncruces/julianday v1.0.0/go.mod h1:Dusn2KvZrrovOMJuOt0TNXL6tB7U2E8kvza5fFc9G7g=
 github.com/ncruces/sort v0.1.6 h1:TrsJfGRH1AoWoaeB4/+gCohot9+cA6u/INaH5agIhNk=
@@ -8,5 +8,5 @@ github.com/tetratelabs/wazero v1.10.1 h1:2DugeJf6VVk58KTPszlNfeeN8AhhpwcZqkJj2ww
 github.com/tetratelabs/wazero v1.10.1/go.mod h1:DRm5twOQ5Gr1AoEdSi0CLjDQF1J9ZAuyqFIjl1KKfQU=
 golang.org/x/sys v0.38.0 h1:3yZWxaJjBmCWXqhN1qh02AkOnCQ1poK6oF+a7xWL6Gc=
 golang.org/x/sys v0.38.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
-golang.org/x/text v0.30.0 h1:yznKA/E9zq54KzlzBEAWn1NXSQ8DIp/NYMy88xJjl4k=
-golang.org/x/text v0.30.0/go.mod h1:yDdHFIX9t+tORqspjENWgzaCVXgk0yYnYuSZ8UzzBVM=
+golang.org/x/text v0.31.0 h1:aC8ghyu4JhP8VojJ2lEHBnochRno1sgL6nEi9WGFGMM=
+golang.org/x/text v0.31.0/go.mod h1:tKRAlv61yKIjGGHX/4tP1LTbc13YSec1pxVEWXzfoeM=
--- a/embed/build.sh
+++ b/embed/build.sh
@@ -23,6 +23,7 @@ trap 'rm -f sqlite3.tmp' EXIT
 	-Wl,--import-undefined \
 	-Wl,--initial-memory=327680 \
 	-D_HAVE_SQLITE_CONFIG_H \
+	-DSQLITE_EXPERIMENTAL_PRAGMA_20251114 \
 	-DSQLITE_CUSTOM_INCLUDE=sqlite_opt.h \
 	$(awk '{print "-Wl,--export="$0}' exports.txt)

--- a/embed/init_test.go
+++ b/embed/init_test.go
@@ -19,7 +19,7 @@ func Test_init(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if version != "3.51.0" {
+	if version != "3.51.1" {
 		t.Error(version)
 	}
 }
--- a/embed/sqlite3.wasm
+++ b/embed/sqlite3.wasm
--- a/gormlite/go.mod
+++ b/gormlite/go.mod
@@ -3,7 +3,7 @@ module github.com/ncruces/go-sqlite3/gormlite
 go 1.24.0

 require (
-	github.com/ncruces/go-sqlite3 v0.30.1
+	github.com/ncruces/go-sqlite3 v0.30.2
 	gorm.io/gorm v1.31.1
 )

--- a/gormlite/go.sum
+++ b/gormlite/go.sum
@@ -2,8 +2,8 @@ github.com/jinzhu/inflection v1.0.0 h1:K317FqzuhWc8YvSVlFMCCUb36O/S9MCKRDI7QkRKD
 github.com/jinzhu/inflection v1.0.0/go.mod h1:h+uFLlag+Qp1Va5pdKtLDYj+kHp5pxUVkryuEj+Srlc=
 github.com/jinzhu/now v1.1.5 h1:/o9tlHleP7gOFmsnYNz3RGnqzefHA47wQpKrrdTIwXQ=
 github.com/jinzhu/now v1.1.5/go.mod h1:d3SSVoowX0Lcu0IBviAWJpolVfI5UJVZZ7cO71lE/z8=
-github.com/ncruces/go-sqlite3 v0.30.1 h1:pHC3YsyRdJv4pCMB4MO1Q2BXw/CAa+Hoj7GSaKtVk+g=
-github.com/ncruces/go-sqlite3 v0.30.1/go.mod h1:UVsWrQaq1qkcal5/vT5lOJnZCVlR5rsThKdwidjFsKc=
+github.com/ncruces/go-sqlite3 v0.30.2 h1:1GVbHAkKAOwjJd3JYl8ldrYROudfZUOah7oXPD7VZbQ=
+github.com/ncruces/go-sqlite3 v0.30.2/go.mod h1:AxKu9sRxkludimFocbktlY6LiYSkxiI5gTA8r+os/Nw=
 github.com/ncruces/julianday v1.0.0 h1:fH0OKwa7NWvniGQtxdJRxAgkBMolni2BjDHaWTxqt7M=
 github.com/ncruces/julianday v1.0.0/go.mod h1:Dusn2KvZrrovOMJuOt0TNXL6tB7U2E8kvza5fFc9G7g=
 github.com/tetratelabs/wazero v1.10.1 h1:2DugeJf6VVk58KTPszlNfeeN8AhhpwcZqkJj2wwFuH8=
--- a/litestream/README.md
+++ b/litestream/README.md
@@ -1,11 +1,26 @@
-# Litestream lightweight read-replicas
+# Litestream in-process replication and lightweight read-replicas

-This package implements the **EXPERIMENTAL** `"litestream"` SQLite VFS
-that offers Litestream [lightweight read-replicas](https://fly.io/blog/litestream-revamped/#lightweight-read-replicas).
+This package adds **EXPERIMENTAL** support for in-process [Litestream](https://litestream.io/).

-See the [example](vfs_test.go) for how to use.
+## Lightweight read-replicas

-To improve performance,
-increase `PollInterval` (and `MinLevel`) as much as you can,
+The `"litestream"` SQLite VFS implements Litestream
+[lightweight read-replicas](https://fly.io/blog/litestream-revamped/#lightweight-read-replicas).
+
+See the [example](example_test.go) for how to use.
+
+To improve performance, increase `PollInterval` as much as you can,
 and set [`PRAGMA cache_size=N`](https://www.sqlite.org/pragma.html#pragma_cache_size)
-(or use `_pragma=cache_size(N)`).
+(or use `_pragma=cache_size(N)`).
+
+## In-process replication
+
+For disaster recovery, it is probably best if you run Litestream as a separate background process,
+as recommended by the [tutorial](https://litestream.io/getting-started/).
+
+However, running Litestream as a background process requires
+compatible locking and cross-process shared memory WAL
+(see our [support matrix](https://github.com/ncruces/go-sqlite3/wiki/Support-matrix)).
+
+If your OS lacks locking or shared memory support,
+you can use `NewPrimary` with the `sqlite3_dotlk` build tag to setup in-process replication.
--- a/litestream/api.go
+++ b/litestream/api.go
@@ -2,6 +2,7 @@
 package litestream

 import (
+	"context"
 	"log/slog"
 	"sync"
 	"time"
@@ -39,16 +40,13 @@ type ReplicaOptions struct {
 	// used by the replica at MinLevel+1.
 	PollInterval time.Duration

-	// Minimum compaction level to track.
-	MinLevel int
-
 	// CacheSize is the maximum size of the page cache in bytes.
 	// Zero means DefaultCacheSize, negative disables caching.
 	CacheSize int
 }

 // NewReplica creates a read-replica from a Litestream client.
-func NewReplica(name string, client litestream.ReplicaClient, options ReplicaOptions) {
+func NewReplica(name string, client ReplicaClient, options ReplicaOptions) {
 	if options.Logger != nil {
 		options.Logger = options.Logger.With("name", name)
 	} else {
@@ -76,3 +74,28 @@ func RemoveReplica(name string) {
 	defer liteMtx.Unlock()
 	delete(liteDBs, name)
 }
+
+// NewPrimary creates a new primary that replicates through client.
+// If restore is not nil, the database is first restored.
+func NewPrimary(ctx context.Context, path string, client ReplicaClient, restore *RestoreOptions) (*litestream.DB, error) {
+	lsdb := litestream.NewDB(path)
+	lsdb.Replica = litestream.NewReplicaWithClient(lsdb, client)
+
+	if restore != nil {
+		err := lsdb.Replica.Restore(ctx, *restore)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	err := lsdb.Open()
+	if err != nil {
+		return nil, err
+	}
+	return lsdb, nil
+}
+
+type (
+	ReplicaClient  = litestream.ReplicaClient
+	RestoreOptions = litestream.RestoreOptions
+)
--- a/litestream/api_test.go
+++ b/litestream/api_test.go
@@ -0,0 +1,104 @@
+package litestream
+
+import (
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/benbjohnson/litestream"
+	"github.com/benbjohnson/litestream/file"
+	"github.com/ncruces/go-sqlite3/driver"
+	_ "github.com/ncruces/go-sqlite3/embed"
+)
+
+func Test_integration(t *testing.T) {
+	dir := t.TempDir()
+	dbpath := filepath.Join(dir, "test.db")
+	backup := filepath.Join(dir, "backup", "test.db")
+
+	db, err := driver.Open(dbpath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	client := file.NewReplicaClient(backup)
+	NewReplica("test.db", client, ReplicaOptions{})
+
+	if err := setupPrimary(t, dbpath, client); err != nil {
+		t.Fatal(err)
+	}
+
+	replica, err := driver.Open("file:test.db?vfs=litestream")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer replica.Close()
+
+	_, err = db.ExecContext(t.Context(), `CREATE TABLE users (id INT, name VARCHAR(10))`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = db.ExecContext(t.Context(),
+		`INSERT INTO users (id, name) VALUES (0, 'go'), (1, 'zig'), (2, 'whatever')`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	time.Sleep(DefaultPollInterval + litestream.DefaultMonitorInterval)
+
+	rows, err := replica.QueryContext(t.Context(), `SELECT id, name FROM users`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer rows.Close()
+
+	row := 0
+	ids := []int{0, 1, 2}
+	names := []string{"go", "zig", "whatever"}
+	for ; rows.Next(); row++ {
+		var id int
+		var name string
+		err := rows.Scan(&id, &name)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if id != ids[row] {
+			t.Errorf("got %d, want %d", id, ids[row])
+		}
+		if name != names[row] {
+			t.Errorf("got %q, want %q", name, names[row])
+		}
+	}
+	if row != 3 {
+		t.Errorf("got %d, want %d", row, len(ids))
+	}
+
+	var lag int
+	err = replica.QueryRowContext(t.Context(), `PRAGMA litestream_lag`).Scan(&lag)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if lag < 0 || lag > 2 {
+		t.Errorf("got %d", lag)
+	}
+
+	var txid string
+	err = replica.QueryRowContext(t.Context(), `PRAGMA litestream_txid`).Scan(&txid)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if txid != "0000000000000001" {
+		t.Errorf("got %q", txid)
+	}
+}
+
+func setupPrimary(tb testing.TB, path string, client ReplicaClient) error {
+	db, err := NewPrimary(tb.Context(), path, client, nil)
+	if err == nil {
+		tb.Cleanup(func() { db.Close(tb.Context()) })
+	}
+	return err
+}
--- a/litestream/go.mod
+++ b/litestream/go.mod
@@ -3,10 +3,11 @@ module github.com/ncruces/go-sqlite3/litestream
 go 1.24.4

 require (
-	github.com/benbjohnson/litestream v0.5.2
-	github.com/ncruces/go-sqlite3 v0.30.1
+	github.com/benbjohnson/litestream v0.5.3-0.20251109214555-48dc960260f0
+	github.com/ncruces/go-sqlite3 v0.30.2
 	github.com/ncruces/wbt v0.2.0
 	github.com/superfly/ltx v0.5.0
+	golang.org/x/sync v0.18.0
 )

 // github.com/ncruces/go-sqlite3
@@ -28,9 +29,9 @@ require (
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/prometheus/client_golang v1.23.2 // indirect
 	github.com/prometheus/client_model v0.6.2 // indirect
-	github.com/prometheus/common v0.67.3 // indirect
+	github.com/prometheus/common v0.67.4 // indirect
 	github.com/prometheus/procfs v0.19.2 // indirect
-	github.com/psanford/sqlite3vfs v0.0.0-20240315230605-24e1d98cf361 // indirect
+	github.com/psanford/sqlite3vfs v0.0.0-20251127171934-4e34e03a991a // indirect
 	go.yaml.in/yaml/v2 v2.4.3 // indirect
 	golang.org/x/crypto v0.45.0 // indirect
 	google.golang.org/protobuf v1.36.10 // indirect
@@ -60,4 +61,4 @@ require (
 	github.com/aws/smithy-go v1.22.5 // indirect
 )

-replace modernc.org/sqlite => github.com/ncruces/go-sqlite3/litestream/modernc v0.0.0-20251109124432-99b097de3b79
+replace modernc.org/sqlite => github.com/ncruces/go-sqlite3/litestream/modernc v0.30.1
--- a/litestream/go.sum
+++ b/litestream/go.sum
@@ -60,8 +60,8 @@ github.com/aws/aws-sdk-go-v2/service/sts v1.35.1 h1:iF4Xxkc0H9c/K2dS0zZw3SCkj0Z7
 github.com/aws/aws-sdk-go-v2/service/sts v1.35.1/go.mod h1:0bxIatfN0aLq4mjoLDeBpOjOke68OsFlXPDFJ7V0MYw=
 github.com/aws/smithy-go v1.22.5 h1:P9ATCXPMb2mPjYBgueqJNCA5S9UfktsW0tTxi+a7eqw=
 github.com/aws/smithy-go v1.22.5/go.mod h1:t1ufH5HMublsJYulve2RKmHDC15xu1f26kHCp/HgceI=
-github.com/benbjohnson/litestream v0.5.2 h1:uD9I17n6RgUgyCwPM/Sw2YXNmMGixecUB5kmJ4FL08o=
-github.com/benbjohnson/litestream v0.5.2/go.mod h1:jSW6AGqbxmJnEXGjMHchlZclGphzbJ6jGrGo5fYIDhU=
+github.com/benbjohnson/litestream v0.5.3-0.20251109214555-48dc960260f0 h1:190qM2axbs1p7NyRm5/ygqrDdcIYhc5QXPTK04Cgyno=
+github.com/benbjohnson/litestream v0.5.3-0.20251109214555-48dc960260f0/go.mod h1:0gjSLi7Qm5INdtdo6YJMFMsS5e/KM2s3CFYF3OtLmY8=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
@@ -113,10 +113,10 @@ github.com/nats-io/nkeys v0.4.11 h1:q44qGV008kYd9W1b1nEBkNzvnWxtRSQ7A8BoqRrcfa0=
 github.com/nats-io/nkeys v0.4.11/go.mod h1:szDimtgmfOi9n25JpfIdGw12tZFYXqhGxjhVxsatHVE=
 github.com/nats-io/nuid v1.0.1 h1:5iA8DT8V7q8WK2EScv2padNa/rTESc1KdnPw4TC2paw=
 github.com/nats-io/nuid v1.0.1/go.mod h1:19wcPz3Ph3q0Jbyiqsd0kePYG7A95tJPxeL+1OSON2c=
-github.com/ncruces/go-sqlite3 v0.30.1 h1:pHC3YsyRdJv4pCMB4MO1Q2BXw/CAa+Hoj7GSaKtVk+g=
-github.com/ncruces/go-sqlite3 v0.30.1/go.mod h1:UVsWrQaq1qkcal5/vT5lOJnZCVlR5rsThKdwidjFsKc=
-github.com/ncruces/go-sqlite3/litestream/modernc v0.0.0-20251109124432-99b097de3b79 h1:evpQceUV2vRbOe84U/QhBBchfqFERRHTx1JOadFFMLE=
-github.com/ncruces/go-sqlite3/litestream/modernc v0.0.0-20251109124432-99b097de3b79/go.mod h1:GSM2gXEOb9HIFFtsl0IUtnpvpDmVi7Kbp8z5GzwA0Tw=
+github.com/ncruces/go-sqlite3 v0.30.2 h1:1GVbHAkKAOwjJd3JYl8ldrYROudfZUOah7oXPD7VZbQ=
+github.com/ncruces/go-sqlite3 v0.30.2/go.mod h1:AxKu9sRxkludimFocbktlY6LiYSkxiI5gTA8r+os/Nw=
+github.com/ncruces/go-sqlite3/litestream/modernc v0.30.1 h1:3SNAOrm+qmLprkZybcvBrVNHyt0QYHljUGxmOXnL+K0=
+github.com/ncruces/go-sqlite3/litestream/modernc v0.30.1/go.mod h1:GSM2gXEOb9HIFFtsl0IUtnpvpDmVi7Kbp8z5GzwA0Tw=
 github.com/ncruces/julianday v1.0.0 h1:fH0OKwa7NWvniGQtxdJRxAgkBMolni2BjDHaWTxqt7M=
 github.com/ncruces/julianday v1.0.0/go.mod h1:Dusn2KvZrrovOMJuOt0TNXL6tB7U2E8kvza5fFc9G7g=
 github.com/ncruces/wbt v0.2.0 h1:Q9zlKOBSZc7Yy/R2cGa35g6RKUUE3BjNIW3tfGC4F04=
@@ -133,16 +133,18 @@ github.com/prometheus/client_golang v1.23.2 h1:Je96obch5RDVy3FDMndoUsjAhG5Edi49h
 github.com/prometheus/client_golang v1.23.2/go.mod h1:Tb1a6LWHB3/SPIzCoaDXI4I8UHKeFTEQ1YCr+0Gyqmg=
 github.com/prometheus/client_model v0.6.2 h1:oBsgwpGs7iVziMvrGhE53c/GrLUsZdHnqNwqPLxwZyk=
 github.com/prometheus/client_model v0.6.2/go.mod h1:y3m2F6Gdpfy6Ut/GBsUqTWZqCUvMVzSfMLjcu6wAwpE=
-github.com/prometheus/common v0.67.3 h1:shd26MlnwTw5jksTDhC7rTQIteBxy+ZZDr3t7F2xN2Q=
-github.com/prometheus/common v0.67.3/go.mod h1:gP0fq6YjjNCLssJCQp0yk4M8W6ikLURwkdd/YKtTbyI=
+github.com/prometheus/common v0.67.4 h1:yR3NqWO1/UyO1w2PhUvXlGQs/PtFmoveVO0KZ4+Lvsc=
+github.com/prometheus/common v0.67.4/go.mod h1:gP0fq6YjjNCLssJCQp0yk4M8W6ikLURwkdd/YKtTbyI=
 github.com/prometheus/procfs v0.19.2 h1:zUMhqEW66Ex7OXIiDkll3tl9a1ZdilUOd/F6ZXw4Vws=
 github.com/prometheus/procfs v0.19.2/go.mod h1:M0aotyiemPhBCM0z5w87kL22CxfcH05ZpYlu+b4J7mw=
-github.com/psanford/sqlite3vfs v0.0.0-20240315230605-24e1d98cf361 h1:vAKifIJuYY306ZJSrwDgKonWcJGELijdaenABqbV03E=
-github.com/psanford/sqlite3vfs v0.0.0-20240315230605-24e1d98cf361/go.mod h1:iW4cSew5PAb1sMZiTEkVJAIBNrepaB6jTYjeP47WtI0=
+github.com/psanford/sqlite3vfs v0.0.0-20251127171934-4e34e03a991a h1:r4YWl0uVObCbBFvj1VsIlyHzgZwZOHvY1KdRaQjzzUc=
+github.com/psanford/sqlite3vfs v0.0.0-20251127171934-4e34e03a991a/go.mod h1:iW4cSew5PAb1sMZiTEkVJAIBNrepaB6jTYjeP47WtI0=
 github.com/rogpeppe/go-internal v1.12.0 h1:exVL4IDcn6na9z1rAb56Vxr+CgyK3nn3O+epU5NdKM8=
 github.com/rogpeppe/go-internal v1.12.0/go.mod h1:E+RYuTGaKKdloAfM02xzb0FW3Paa99yedzYV+kq4uf4=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+github.com/studio-b12/gowebdav v0.11.0 h1:qbQzq4USxY28ZYsGJUfO5jR+xkFtcnwWgitp4Zp1irU=
+github.com/studio-b12/gowebdav v0.11.0/go.mod h1:bHA7t77X/QFExdeAnDzK6vKM34kEZAcE1OX4MfiwjkE=
 github.com/superfly/ltx v0.5.0 h1:dXNrcT3ZtMb6iKZopIV7z5UBscnapg0b0F02loQsk5o=
 github.com/superfly/ltx v0.5.0/go.mod h1:Nf50QAIXU/ET4ua3AuQ2fh31MbgNQZA7r/DYx6Os77s=
 github.com/tetratelabs/wazero v1.10.1 h1:2DugeJf6VVk58KTPszlNfeeN8AhhpwcZqkJj2wwFuH8=
@@ -169,8 +171,8 @@ golang.org/x/net v0.47.0 h1:Mx+4dIFzqraBXUugkia1OOvlD6LemFo1ALMHjrXDOhY=
 golang.org/x/net v0.47.0/go.mod h1:/jNxtkgq5yWUGYkaZGqo27cfGZ1c5Nen03aYrrKpVRU=
 golang.org/x/oauth2 v0.32.0 h1:jsCblLleRMDrxMN29H3z/k1KliIvpLgCkE6R8FXXNgY=
 golang.org/x/oauth2 v0.32.0/go.mod h1:lzm5WQJQwKZ3nwavOZ3IS5Aulzxi68dUSgRHujetwEA=
-golang.org/x/sync v0.17.0 h1:l60nONMj9l5drqw6jlhIELNv9I0A4OFgRsG9k2oT9Ug=
-golang.org/x/sync v0.17.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
+golang.org/x/sync v0.18.0 h1:kr88TuHDroi+UVf+0hZnirlk8o8T+4MrK6mr60WkH/I=
+golang.org/x/sync v0.18.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
 golang.org/x/sys v0.38.0 h1:3yZWxaJjBmCWXqhN1qh02AkOnCQ1poK6oF+a7xWL6Gc=
 golang.org/x/sys v0.38.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
 golang.org/x/text v0.31.0 h1:aC8ghyu4JhP8VojJ2lEHBnochRno1sgL6nEi9WGFGMM=
--- a/litestream/modernc/go.mod
+++ b/litestream/modernc/go.mod
@@ -2,7 +2,7 @@ module modernc.org/sqlite

 go 1.24.0

-require github.com/ncruces/go-sqlite3 v0.30.1
+require github.com/ncruces/go-sqlite3 v0.30.2

 require (
 	github.com/ncruces/julianday v1.0.0 // indirect
--- a/litestream/modernc/go.sum
+++ b/litestream/modernc/go.sum
@@ -1,10 +1,10 @@
-github.com/ncruces/go-sqlite3 v0.30.1 h1:pHC3YsyRdJv4pCMB4MO1Q2BXw/CAa+Hoj7GSaKtVk+g=
-github.com/ncruces/go-sqlite3 v0.30.1/go.mod h1:UVsWrQaq1qkcal5/vT5lOJnZCVlR5rsThKdwidjFsKc=
+github.com/ncruces/go-sqlite3 v0.30.2 h1:1GVbHAkKAOwjJd3JYl8ldrYROudfZUOah7oXPD7VZbQ=
+github.com/ncruces/go-sqlite3 v0.30.2/go.mod h1:AxKu9sRxkludimFocbktlY6LiYSkxiI5gTA8r+os/Nw=
 github.com/ncruces/julianday v1.0.0 h1:fH0OKwa7NWvniGQtxdJRxAgkBMolni2BjDHaWTxqt7M=
 github.com/ncruces/julianday v1.0.0/go.mod h1:Dusn2KvZrrovOMJuOt0TNXL6tB7U2E8kvza5fFc9G7g=
 github.com/tetratelabs/wazero v1.10.1 h1:2DugeJf6VVk58KTPszlNfeeN8AhhpwcZqkJj2wwFuH8=
 github.com/tetratelabs/wazero v1.10.1/go.mod h1:DRm5twOQ5Gr1AoEdSi0CLjDQF1J9ZAuyqFIjl1KKfQU=
 golang.org/x/sys v0.38.0 h1:3yZWxaJjBmCWXqhN1qh02AkOnCQ1poK6oF+a7xWL6Gc=
 golang.org/x/sys v0.38.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
-golang.org/x/text v0.30.0 h1:yznKA/E9zq54KzlzBEAWn1NXSQ8DIp/NYMy88xJjl4k=
-golang.org/x/text v0.30.0/go.mod h1:yDdHFIX9t+tORqspjENWgzaCVXgk0yYnYuSZ8UzzBVM=
+golang.org/x/text v0.31.0 h1:aC8ghyu4JhP8VojJ2lEHBnochRno1sgL6nEi9WGFGMM=
+golang.org/x/text v0.31.0/go.mod h1:tKRAlv61yKIjGGHX/4tP1LTbc13YSec1pxVEWXzfoeM=
--- a/litestream/vfs.go
+++ b/litestream/vfs.go
@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"strconv"
 	"sync"
 	"time"

@@ -160,6 +161,34 @@ func (f *liteFile) DeviceCharacteristics() vfs.DeviceCharacteristic {
 	return 0
 }

+func (f *liteFile) Pragma(name, value string) (string, error) {
+	switch name {
+	case "litestream_txid":
+		txid := f.txid
+		if txid == 0 {
+			// Outside transaction.
+			f.db.mtx.Lock()
+			txid = f.db.txids[0]
+			f.db.mtx.Unlock()
+		}
+		return txid.String(), nil
+
+	case "litestream_lag":
+		f.db.mtx.Lock()
+		lastPoll := f.db.lastPoll
+		f.db.mtx.Unlock()
+
+		if lastPoll.IsZero() {
+			// Never polled successfully.
+			return "-1", nil
+		}
+		lag := time.Since(lastPoll) / time.Second
+		return strconv.FormatInt(int64(lag), 10), nil
+	}
+
+	return "", sqlite3.NOTFOUND
+}
+
 func (f *liteFile) SetDB(conn any) {
 	f.conn = conn.(*sqlite3.Conn)
 }
@@ -219,7 +248,7 @@ func (f *liteDB) pollReplica(ctx context.Context) (*pageIndex, ltx.TXID, error)
 		return f.pages, f.txids[0], nil
 	}

-	for level := range pollLevels(f.opts.MinLevel) {
+	for level := range []int{0, 1, litestream.SnapshotLevel} {
 		if err := f.updateLevel(ctx, level); err != nil {
 			f.opts.Logger.Error("cannot poll replica", "error", err)
 			return nil, 0, err
@@ -284,26 +313,10 @@ func (f *liteDB) updateInfo(ctx context.Context, info *ltx.FileInfo) error {
 	// Track the MaxTXID for each level.
 	maxTXID := &f.txids[info.Level]
 	*maxTXID = max(*maxTXID, info.MaxTXID)
+	f.txids[0] = max(f.txids[0], *maxTXID)
 	return nil
 }

-func pollLevels(minLevel int) (r []int) {
-	// Updating from lower to upper levels is non-racy,
-	// since LTX files are compacted into higher levels
-	// before the lower level LTX files are deleted.
-
-	// Also, only level 0 compactions and snapshots delete files,
-	// so the intermediate levels never need to be updated.
-
-	if minLevel <= 0 {
-		return append(r, 0, 1, litestream.SnapshotLevel)
-	}
-	if minLevel >= litestream.SnapshotLevel {
-		return append(r, litestream.SnapshotLevel)
-	}
-	return append(r, minLevel, litestream.SnapshotLevel)
-}
-
 // Type aliases; these are a mouthful.
 type pageIndex = wbt.Tree[uint32, ltx.PageIndexElem]
 type levelTXIDs = [litestream.SnapshotLevel + 1]ltx.TXID
--- a/litestream/vfs_test.go
+++ b/litestream/vfs_test.go
@@ -1,34 +0,0 @@
-package litestream
-
-import (
-	"slices"
-	"strconv"
-	"testing"
-
-	"github.com/benbjohnson/litestream"
-
-	_ "github.com/ncruces/go-sqlite3/embed"
-)
-
-func Test_pollLevels(t *testing.T) {
-	tests := []struct {
-		minLevel int
-		want     []int
-	}{
-		{minLevel: -1, want: []int{0, 1, litestream.SnapshotLevel}},
-		{minLevel: 0, want: []int{0, 1, litestream.SnapshotLevel}},
-		{minLevel: 1, want: []int{1, litestream.SnapshotLevel}},
-		{minLevel: 2, want: []int{2, litestream.SnapshotLevel}},
-		{minLevel: 3, want: []int{3, litestream.SnapshotLevel}},
-		{minLevel: litestream.SnapshotLevel, want: []int{litestream.SnapshotLevel}},
-		{minLevel: litestream.SnapshotLevel + 1, want: []int{litestream.SnapshotLevel}},
-	}
-	for _, tt := range tests {
-		t.Run(strconv.Itoa(tt.minLevel), func(t *testing.T) {
-			got := pollLevels(tt.minLevel)
-			if !slices.Equal(got, tt.want) {
-				t.Errorf("pollLevels() = %v, want %v", got, tt.want)
-			}
-		})
-	}
-}
--- a/sqlite3/download.sh
+++ b/sqlite3/download.sh
@@ -3,11 +3,11 @@ set -euo pipefail

 cd -P -- "$(dirname -- "$0")"

-curl -#OL "https://sqlite.org/2025/sqlite-autoconf-3510000.tar.gz"
+curl -#OL "https://sqlite.org/2025/sqlite-autoconf-3510100.tar.gz"

 # Verify download.
 if hash=$(openssl dgst -sha3-256 sqlite-autoconf-*.tar.gz); then
-  if ! [[ $hash =~ fa52f9cc74dbca004aa650ae698036a3350611f672649e165078f4eae21d6a2e ]]; then
+  if ! [[ $hash =~ 9b2b1e73f577def1d5b75c5541555a7f42e6e073ad19f7a9118478389c9bbd9b ]]; then
    echo $hash
    exit 1
  fi
@@ -23,7 +23,7 @@ mv sqlite-*/sqlite3.h .
 mv sqlite-*/sqlite3ext.h .
 rm -r sqlite-*

-GITHUB_TAG="https://github.com/sqlite/sqlite/raw/version-3.51.0"
+GITHUB_TAG="https://github.com/sqlite/sqlite/raw/version-3.51.1"

 mkdir -p ext/
 cd ext/
--- a/sqlite3/libc/libc.wasm
+++ b/sqlite3/libc/libc.wasm
--- a/sqlite3/libc/libc.wat
+++ b/sqlite3/libc/libc.wat
@@ -4,7 +4,8 @@
 (type $2 (func (param i32 i32 i32 i32)))
 (type $3 (func (param i32) (result i32)))
 (memory $0 256)
- (data $0 (i32.const 4096) "\01")
+ (data $.data (i32.const 4097) "\10\00\00\01\00\00\00\00\00\00\00\0c\10\00\00\0c\10\00\00\0c\10")
+ (data $.data.1 (i32.const 4157) "\10\00\00\00\10")
 (table $0 1 1 funcref)
 (export "memory" (memory $0))
 (export "qsort" (func $qsort))
@@ -1493,33 +1494,243 @@
  (local $2 i32)
  (local $3 i32)
  (local $4 i32)
-  (local $5 i32)
+  (local $5 v128)
  (local $6 v128)
  (local $7 v128)
  (local $8 v128)
-  (local $9 v128)
-  (block $block
-   (if
-    (local.tee $3
-     (i32.load8_u
-      (local.get $1)
+  (block $block2
+   (block $block
+    (br_if $block
+     (i32.eqz
+      (local.tee $3
+       (i32.load8_u
+        (local.get $1)
+       )
+      )
     )
    )
-    (then
-     (br_if $block
+    (br_if $block
+     (i32.eqz
      (i32.load8_u offset=1
       (local.get $1)
      )
     )
    )
+    (loop $label
+     (v128.store
+      (i32.const 4080)
+      (local.get $6)
+     )
+     (i32.store8
+      (i32.or
+       (local.tee $3
+        (i32.and
+         (local.tee $2
+          (i32.load8_u
+           (local.get $1)
+          )
+         )
+         (i32.const 15)
+        )
+       )
+       (i32.const 4080)
+      )
+      (i32.or
+       (i32.load8_u
+        (i32.or
+         (local.get $3)
+         (i32.const 4080)
+        )
+       )
+       (i32.shl
+        (i32.const 1)
+        (i32.sub
+         (local.tee $4
+          (i32.shr_u
+           (local.get $2)
+           (i32.const 4)
+          )
+         )
+         (i32.const 8)
+        )
+       )
+      )
+     )
+     (v128.store
+      (i32.const 4064)
+      (local.get $5)
+     )
+     (i32.store8
+      (local.tee $3
+       (i32.or
+        (local.get $3)
+        (i32.const 4064)
+       )
+      )
+      (i32.or
+       (i32.load8_u
+        (local.get $3)
+       )
+       (i32.shl
+        (i32.const 1)
+        (local.get $4)
+       )
+      )
+     )
+     (local.set $1
+      (i32.add
+       (local.get $1)
+       (i32.const 1)
+      )
+     )
+     (local.set $6
+      (v128.load
+       (i32.const 4080)
+      )
+     )
+     (local.set $5
+      (v128.load
+       (i32.const 4064)
+      )
+     )
+     (br_if $label
+      (local.get $2)
+     )
+    )
+    (block $block1
+     (if
+      (v128.any_true
+       (local.tee $7
+        (v128.and
+         (v128.or
+          (i8x16.swizzle
+           (local.get $6)
+           (v128.xor
+            (local.tee $8
+             (v128.and
+              (local.tee $7
+               (v128.load
+                (local.tee $2
+                 (i32.and
+                  (local.get $0)
+                  (i32.const -16)
+                 )
+                )
+               )
+              )
+              (v128.const i32x4 0x8f8f8f8f 0x8f8f8f8f 0x8f8f8f8f 0x8f8f8f8f)
+             )
+            )
+            (v128.const i32x4 0x80808080 0x80808080 0x80808080 0x80808080)
+           )
+          )
+          (i8x16.swizzle
+           (local.get $5)
+           (local.get $8)
+          )
+         )
+         (i8x16.swizzle
+          (v128.const i32x4 0x08040201 0x80402010 0x08040201 0x80402010)
+          (i8x16.shr_u
+           (local.get $7)
+           (i32.const 4)
+          )
+         )
+        )
+       )
+      )
+      (then
+       (br_if $block1
+        (local.tee $1
+         (i32.and
+          (i32.xor
+           (i8x16.bitmask
+            (i8x16.eq
+             (local.get $7)
+             (v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000)
+            )
+           )
+           (i32.const 65535)
+          )
+          (i32.shl
+           (i32.const -1)
+           (i32.and
+            (local.get $0)
+            (i32.const 15)
+           )
+          )
+         )
+        )
+       )
+      )
+     )
+     (loop $label1
+      (br_if $label1
+       (i32.eqz
+        (v128.any_true
+         (local.tee $7
+          (v128.and
+           (v128.or
+            (i8x16.swizzle
+             (local.get $6)
+             (v128.xor
+              (local.tee $8
+               (v128.and
+                (local.tee $7
+                 (v128.load
+                  (local.tee $2
+                   (i32.add
+                    (local.get $2)
+                    (i32.const 16)
+                   )
+                  )
+                 )
+                )
+                (v128.const i32x4 0x8f8f8f8f 0x8f8f8f8f 0x8f8f8f8f 0x8f8f8f8f)
+               )
+              )
+              (v128.const i32x4 0x80808080 0x80808080 0x80808080 0x80808080)
+             )
+            )
+            (i8x16.swizzle
+             (local.get $5)
+             (local.get $8)
+            )
+           )
+           (i8x16.swizzle
+            (v128.const i32x4 0x08040201 0x80402010 0x08040201 0x80402010)
+            (i8x16.shr_u
+             (local.get $7)
+             (i32.const 4)
+            )
+           )
+          )
+         )
+        )
+       )
+      )
+     )
+     (local.set $1
+      (i32.xor
+       (i8x16.bitmask
+        (i8x16.eq
+         (local.get $7)
+         (v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000)
+        )
+       )
+       (i32.const 65535)
+      )
+     )
+    )
+    (br $block2)
   )
-   (block $block1
+   (block $block3
    (if
     (v128.any_true
-      (local.tee $6
+      (local.tee $5
       (v128.or
        (i8x16.eq
-         (local.tee $7
+         (local.tee $6
          (v128.load
           (local.tee $2
            (i32.and
@@ -1532,8 +1743,8 @@
         (v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000)
        )
        (i8x16.eq
-         (local.get $7)
-         (local.tee $7
+         (local.get $6)
+         (local.tee $6
          (i8x16.splat
           (local.get $3)
          )
@@ -1543,11 +1754,11 @@
      )
     )
     (then
-      (br_if $block1
+      (br_if $block3
       (local.tee $1
        (i32.and
         (i8x16.bitmask
-          (local.get $6)
+          (local.get $5)
         )
         (i32.shl
          (i32.const -1)
@@ -1561,14 +1772,14 @@
      )
     )
    )
-    (loop $label
-     (br_if $label
+    (loop $label2
+     (br_if $label2
      (i32.eqz
       (v128.any_true
-        (local.tee $6
+        (local.tee $5
         (v128.or
          (i8x16.eq
-           (local.tee $6
+           (local.tee $5
            (v128.load
             (local.tee $2
              (i32.add
@@ -1581,8 +1792,8 @@
           (v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000)
          )
          (i8x16.eq
+           (local.get $5)
           (local.get $6)
-           (local.get $7)
          )
         )
        )
@@ -1592,230 +1803,10 @@
    )
    (local.set $1
     (i8x16.bitmask
-      (local.get $6)
-     )
-    )
-   )
-   (return
-    (i32.add
-     (i32.ctz
-      (local.get $1)
-     )
-     (i32.sub
-      (local.get $2)
-      (local.get $0)
-     )
-    )
-   )
-  )
-  (local.set $4
-   (i32.and
-    (local.get $0)
-    (i32.const 15)
-   )
-  )
-  (loop $label1
-   (v128.store
-    (i32.const 4080)
-    (local.get $7)
-   )
-   (i32.store8
-    (i32.or
-     (local.tee $3
-      (i32.and
-       (local.tee $2
-        (i32.load8_u
-         (local.get $1)
-        )
-       )
-       (i32.const 15)
-      )
-     )
-     (i32.const 4080)
-    )
-    (i32.or
-     (i32.load8_u
-      (i32.or
-       (local.get $3)
-       (i32.const 4080)
-      )
-     )
-     (i32.shl
-      (i32.const 1)
-      (i32.sub
-       (local.tee $5
-        (i32.shr_u
-         (local.get $2)
-         (i32.const 4)
-        )
-       )
-       (i32.const 8)
-      )
-     )
-    )
-   )
-   (v128.store
-    (i32.const 4064)
-    (local.get $6)
-   )
-   (i32.store8
-    (local.tee $3
-     (i32.or
-      (local.get $3)
-      (i32.const 4064)
-     )
-    )
-    (i32.or
-     (i32.load8_u
-      (local.get $3)
-     )
-     (i32.shl
-      (i32.const 1)
      (local.get $5)
     )
    )
   )
-   (local.set $1
-    (i32.add
-     (local.get $1)
-     (i32.const 1)
-    )
-   )
-   (local.set $7
-    (v128.load
-     (i32.const 4080)
-    )
-   )
-   (local.set $6
-    (v128.load
-     (i32.const 4064)
-    )
-   )
-   (br_if $label1
-    (local.get $2)
-   )
-  )
-  (block $block2
-   (if
-    (v128.any_true
-     (local.tee $8
-      (v128.and
-       (v128.or
-        (i8x16.swizzle
-         (local.get $7)
-         (v128.xor
-          (local.tee $9
-           (v128.and
-            (local.tee $8
-             (v128.load
-              (local.tee $2
-               (i32.and
-                (local.get $0)
-                (i32.const -16)
-               )
-              )
-             )
-            )
-            (v128.const i32x4 0x8f8f8f8f 0x8f8f8f8f 0x8f8f8f8f 0x8f8f8f8f)
-           )
-          )
-          (v128.const i32x4 0x80808080 0x80808080 0x80808080 0x80808080)
-         )
-        )
-        (i8x16.swizzle
-         (local.get $6)
-         (local.get $9)
-        )
-       )
-       (i8x16.swizzle
-        (v128.const i32x4 0x08040201 0x80402010 0x08040201 0x80402010)
-        (i8x16.shr_u
-         (local.get $8)
-         (i32.const 4)
-        )
-       )
-      )
-     )
-    )
-    (then
-     (br_if $block2
-      (local.tee $1
-       (i32.and
-        (i32.xor
-         (i8x16.bitmask
-          (i8x16.eq
-           (local.get $8)
-           (v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000)
-          )
-         )
-         (i32.const 65535)
-        )
-        (i32.shl
-         (i32.const -1)
-         (local.get $4)
-        )
-       )
-      )
-     )
-    )
-   )
-   (loop $label2
-    (br_if $label2
-     (i32.eqz
-      (v128.any_true
-       (local.tee $8
-        (v128.and
-         (v128.or
-          (i8x16.swizzle
-           (local.get $7)
-           (v128.xor
-            (local.tee $9
-             (v128.and
-              (local.tee $8
-               (v128.load
-                (local.tee $2
-                 (i32.add
-                  (local.get $2)
-                  (i32.const 16)
-                 )
-                )
-               )
-              )
-              (v128.const i32x4 0x8f8f8f8f 0x8f8f8f8f 0x8f8f8f8f 0x8f8f8f8f)
-             )
-            )
-            (v128.const i32x4 0x80808080 0x80808080 0x80808080 0x80808080)
-           )
-          )
-          (i8x16.swizzle
-           (local.get $6)
-           (local.get $9)
-          )
-         )
-         (i8x16.swizzle
-          (v128.const i32x4 0x08040201 0x80402010 0x08040201 0x80402010)
-          (i8x16.shr_u
-           (local.get $8)
-           (i32.const 4)
-          )
-         )
-        )
-       )
-      )
-     )
-    )
-   )
-   (local.set $1
-    (i32.xor
-     (i8x16.bitmask
-      (i8x16.eq
-       (local.get $8)
-       (v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000)
-      )
-     )
-     (i32.const 65535)
-    )
-   )
  )
  (i32.add
   (i32.ctz
--- a/vfs/memdb/memdb.go
+++ b/vfs/memdb/memdb.go
@@ -223,7 +223,7 @@ func (m *memFile) Lock(lock vfs.LockLevel) error {
 		m.reserved = true

 	case vfs.LOCK_EXCLUSIVE:
-		if m.lock < vfs.LOCK_PENDING {
+		if m.lock == vfs.LOCK_RESERVED {
 			m.lock = vfs.LOCK_PENDING
 			m.pending = true
 		}
--- a/vfs/mvcc/mvcc.go
+++ b/vfs/mvcc/mvcc.go
@@ -252,9 +252,8 @@ func (m *mvccFile) Lock(lock vfs.LockLevel) error {
 		}
 		defer time.AfterFunc(time.Millisecond, m.waiter.Broadcast).Stop()
 		for m.owner != nil {
-			// Our snapshot is invalid.
 			if m.data != nil && m.data != m.mvccDB.data {
-				return sqlite3.BUSY_SNAPSHOT
+				return sqlite3.BUSY_SNAPSHOT // Our snapshot is invalid.
 			}
 			if time.Since(before) > time.Millisecond {
 				return sqlite3.BUSY
@@ -266,17 +265,16 @@ func (m *mvccFile) Lock(lock vfs.LockLevel) error {
 	case m.data == nil:
 		m.data = m.mvccDB.data
 	case m.data != m.mvccDB.data:
-		// Our snapshot is invalid.
-		return sqlite3.BUSY_SNAPSHOT
+		return sqlite3.BUSY_SNAPSHOT // Our snapshot is invalid.
 	}
 	// Take ownership.
-	m.wrflag = false
 	m.lock = lock
 	m.owner = m
 	return nil
 }

 func (m *mvccFile) Unlock(lock vfs.LockLevel) error {
+	m.wrflag = false // SQLite calls unlock even if locking is unsuccessful.
 	if m.lock <= lock {
 		return nil
 	}
@@ -287,7 +285,9 @@ func (m *mvccFile) Unlock(lock vfs.LockLevel) error {
 	// Relase ownership, commit changes.
 	if m.owner == m {
 		m.owner = nil
-		m.mvccDB.data = m.data
+		if m.lock == vfs.LOCK_EXCLUSIVE {
+			m.mvccDB.data = m.data
+		}
 		if m.waiter != nil {
 			m.waiter.Broadcast()
 		}
--- a/vfs/shm_copy.go
+++ b/vfs/shm_copy.go
@@ -35,44 +35,38 @@ func (s *vfsShm) shmAcquire(errp *error) {
 	if errp != nil && *errp != nil {
 		return
 	}
-	if len(s.ptrs) == 0 {
+	if len(s.ptrs) == 0 || shmEqual(s.shadow[0][:], s.shared[0][:]) {
 		return
 	}
-	if !shmCopyHeader(
-		util.View(s.mod, s.ptrs[0], _WALINDEX_HDR_SIZE),
-		s.shadow[0][:],
-		s.shared[0][:]) {
-		return
-	}
-
-	skip := _WALINDEX_HDR_SIZE
-	for id := range s.ptrs {
-		shmCopyTables(
-			util.View(s.mod, s.ptrs[id], _WALINDEX_PGSZ)[skip:],
-			s.shadow[id][skip:],
-			s.shared[id][skip:])
-		skip = 0
+	// Copies modified words from shared to private memory.
+	for id, p := range s.ptrs {
+		shared := shmPage(s.shared[id][:])
+		shadow := shmPage(s.shadow[id][:])
+		privat := shmPage(util.View(s.mod, p, _WALINDEX_PGSZ))
+		for i, shared := range shared {
+			if shadow[i] != shared {
+				shadow[i] = shared
+				privat[i] = shared
+			}
+		}
 	}
 }

 func (s *vfsShm) shmRelease() {
-	if len(s.ptrs) == 0 {
+	if len(s.ptrs) == 0 || shmEqual(s.shadow[0][:], util.View(s.mod, s.ptrs[0], _WALINDEX_HDR_SIZE)) {
 		return
 	}
-	if !shmCopyHeader(
-		s.shared[0][:],
-		s.shadow[0][:],
-		util.View(s.mod, s.ptrs[0], _WALINDEX_HDR_SIZE)) {
-		return
-	}
-
-	skip := _WALINDEX_HDR_SIZE
-	for id := range s.ptrs {
-		shmCopyTables(
-			s.shared[id][skip:],
-			s.shadow[id][skip:],
-			util.View(s.mod, s.ptrs[id], _WALINDEX_PGSZ)[skip:])
-		skip = 0
+	// Copies modified words from private to shared memory.
+	for id, p := range s.ptrs {
+		shared := shmPage(s.shared[id][:])
+		shadow := shmPage(s.shadow[id][:])
+		privat := shmPage(util.View(s.mod, p, _WALINDEX_PGSZ))
+		for i, privat := range privat {
+			if shadow[i] != privat {
+				shadow[i] = privat
+				shared[i] = privat
+			}
+		}
 	}
 }

@@ -83,40 +77,11 @@ func (s *vfsShm) shmBarrier() {
 	s.Unlock()
 }

-func shmCopyTables(v1, v2, v3 []byte) {
-	if string(v2) != string(v3) {
-		copy(v1, v3)
-		copy(v2, v3)
-	}
+func shmPage(s []byte) *[_WALINDEX_PGSZ / 4]uint32 {
+	p := (*uint32)(unsafe.Pointer(unsafe.SliceData(s)))
+	return (*[_WALINDEX_PGSZ / 4]uint32)(unsafe.Slice(p, _WALINDEX_PGSZ/4))
 }

-func shmCopyHeader(s1, s2, s3 []byte) (ret bool) {
-	// First copy of the WAL Index Information.
-	if string(s2[:48]) != string(s3[:48]) {
-		copy(s1, s3[:48])
-		copy(s2, s3[:48])
-		ret = true
-	}
-	// Second copy of the WAL Index Information.
-	if string(s2[48:][:48]) != string(s3[48:][:48]) {
-		copy(s1[48:], s3[48:][:48])
-		copy(s2[48:], s3[48:][:48])
-		ret = true
-	}
-	// Checkpoint Information and Locks.
-	i1 := shmCheckpointInfo(s1)
-	i2 := shmCheckpointInfo(s2)
-	for i, i3 := range shmCheckpointInfo(s3) {
-		if i2[i] != i3 {
-			i1[i] = i3
-			i2[i] = i3
-			ret = true
-		}
-	}
-	return
-}
-
-func shmCheckpointInfo(s []byte) *[10]uint32 {
-	p := (*uint32)(unsafe.Pointer(&s[96]))
-	return (*[10]uint32)(unsafe.Slice(p, 10))
+func shmEqual(v1, v2 []byte) bool {
+	return *(*[_WALINDEX_HDR_SIZE]byte)(v1[:]) == *(*[_WALINDEX_HDR_SIZE]byte)(v2[:])
 }
--- a/vfs/tests/mptest/wasm/mptest.wasm
+++ b/vfs/tests/mptest/wasm/mptest.wasm
--- a/vfs/tests/speedtest1/wasm/speedtest1.wasm
+++ b/vfs/tests/speedtest1/wasm/speedtest1.wasm
Author	SHA1	Message	Date
Nuno Cruces	7028e3a5b9	SQLite 3.51.1.	2025-11-30 10:24:34 +00:00
Nuno Cruces	03bb20de6e	Lock tweaks.	2025-11-29 16:12:29 +00:00
Nuno Cruces	20a51a344e	Remove MinLevel.	2025-11-27 17:29:47 +00:00
Nuno Cruces	2dbcc480f7	Initial pragma support.	2025-11-27 16:28:16 +00:00
Nuno Cruces	0f0716c438	Inprocess Litestream primary.	2025-11-26 14:07:44 +00:00