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Readonly WAL.

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This commit is contained in:
Nuno Cruces
2024-04-13 13:43:24 +01:00
parent 46086916d4
commit cc0b011e8d
6 changed files with 55 additions and 17 deletions
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10
internal/util/mmap.go
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@@ -1,4 +1,4 @@
//go:build (darwin || linux || illumos) && (amd64 || arm64) && !sqlite3_flock && !sqlite3_noshm && !sqlite3_nosys
//go:build (darwin || linux || illumos) && (amd64 || arm64 || riscv64) && !sqlite3_flock && !sqlite3_noshm && !sqlite3_nosys
package util
@@ -69,10 +69,10 @@ type MappedRegion struct {
used bool
}
func MapRegion(ctx context.Context, mod api.Module, f *os.File, offset int64, size int32) (*MappedRegion, error) {
func MapRegion(ctx context.Context, mod api.Module, f *os.File, offset int64, size int32, prot int) (*MappedRegion, error) {
s := ctx.Value(moduleKey{}).(*moduleState)
r := s.new(ctx, mod, size)
err := r.mmap(f, offset)
err := r.mmap(f, offset, prot)
if err != nil {
return nil, err
}
@@ -90,9 +90,9 @@ func (r *MappedRegion) Unmap() error {
return err
}
func (r *MappedRegion) mmap(f *os.File, offset int64) error {
func (r *MappedRegion) mmap(f *os.File, offset int64, prot int) error {
_, err := mmap(r.addr, uintptr(r.size),
unix.PROT_READ|unix.PROT_WRITE, unix.MAP_SHARED|unix.MAP_FIXED,
prot, unix.MAP_SHARED|unix.MAP_FIXED,
int(f.Fd()), offset)
r.used = err == nil
return err

2
internal/util/mmap_other.go
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@@ -1,4 +1,4 @@
//go:build !(darwin || linux || illumos) || !(amd64 || arm64) || sqlite3_flock || sqlite3_noshm || sqlite3_nosys
//go:build !(darwin || linux || illumos) || !(amd64 || arm64 || riscv64) || sqlite3_flock || sqlite3_noshm || sqlite3_nosys
package util

32
tests/wal_test.go
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@@ -1,10 +1,12 @@
package tests
import (
"os"
"path/filepath"
"testing"
"github.com/ncruces/go-sqlite3"
"github.com/ncruces/go-sqlite3/vfs"
)
func TestWAL_enter_exit(t *testing.T) {
@@ -32,6 +34,36 @@ func TestWAL_enter_exit(t *testing.T) {
}
}
func TestWAL_readonly(t *testing.T) {
if !vfs.SupportsSharedMemory {
t.Skip("skipping without shared memory")
}
t.Parallel()
tmp := filepath.Join(t.TempDir(), "test.db")
err := os.WriteFile(tmp, waldb, 0666)
if err != nil {
t.Fatal(err)
}
db, err := sqlite3.OpenFlags(tmp, sqlite3.OPEN_READONLY)
if err != nil {
t.Fatal(err)
}
defer db.Close()
stmt, _, err := db.Prepare(`SELECT * FROM sqlite_master`)
if err != nil {
t.Fatal(err)
}
defer stmt.Close()
if stmt.Step() {
t.Error("want no rows")
}
}
func TestConn_WalCheckpoint(t *testing.T) {
t.Parallel()

9
vfs/README.md
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@@ -49,19 +49,18 @@ On 64-bit Linux, macOS and illumos, this module uses `mmap` to implement
[shared-memory for the WAL-index](https://sqlite.org/wal.html#implementation_of_shared_memory_for_the_wal_index),
like SQLite.
To allow `mmap` to work, each connection needs to reserve a lot of address space.\
To allow `mmap` to work, each connection needs to reserve up to 4GB of address space.\
To limit the amount of address space each connection needs,
use [`WithMemoryLimitPages`](../tests/parallel/parallel_test.go#L21).
On all other platforms, [WAL](https://sqlite.org/wal.html) support is
[limited](https://sqlite.org/wal.html#noshm).
To work around that limitation, SQLite is [patched](sqlite3/locking_mode.patch)
To work around this limitation, SQLite is [patched](sqlite3/locking_mode.patch)
to automatically use `EXCLUSIVE` locking mode for WAL databases on such platforms.
Because connection pooling is incompatible with `EXCLUSIVE` locking mode,
to use the [`database/sql`](https://pkg.go.dev/database/sql) driver
with WAL mode databases you should disable connection pooling by calling
To use the [`database/sql`](https://pkg.go.dev/database/sql) driver
with `EXCLUSIVE` locking mode you should disable connection pooling by calling
[`db.SetMaxOpenConns(1)`](https://pkg.go.dev/database/sql#DB.SetMaxOpenConns).
You can use [`vfs.SupportsSharedMemory`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/vfs#SupportsSharedMemory)

17
vfs/shm.go
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@@ -1,4 +1,4 @@
//go:build (linux || darwin) && (amd64 || arm64) && !sqlite3_flock && !sqlite3_noshm && !sqlite3_nosys
//go:build (darwin || linux || illumos) && (amd64 || arm64 || riscv64) && !sqlite3_flock && !sqlite3_noshm && !sqlite3_nosys
package vfs
@@ -42,11 +42,12 @@ func (f *vfsFile) shmMap(ctx context.Context, mod api.Module, id, size int32, ex
if f.shm.File == nil {
var flag int
if f.readOnly {
flag = unix.O_RDONLY | unix.O_NOFOLLOW
flag = unix.O_RDONLY
} else {
flag = unix.O_RDWR | unix.O_CREAT | unix.O_NOFOLLOW
flag = unix.O_RDWR
}
s, err := os.OpenFile(f.Name()+"-shm", flag, 0666)
s, err := os.OpenFile(f.Name()+"-shm",
flag|unix.O_CREAT|unix.O_NOFOLLOW, 0666)
if err != nil {
return 0, _CANTOPEN
}
@@ -88,7 +89,13 @@ func (f *vfsFile) shmMap(ctx context.Context, mod api.Module, id, size int32, ex
}
}
r, err := util.MapRegion(ctx, mod, f.shm.File, int64(id)*int64(size), size)
var prot int
if f.readOnly {
prot = unix.PROT_READ
} else {
prot = unix.PROT_READ | unix.PROT_WRITE
}
r, err := util.MapRegion(ctx, mod, f.shm.File, int64(id)*int64(size), size, prot)
if err != nil {
return 0, err
}

2
vfs/shm_other.go
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@@ -1,4 +1,4 @@
//go:build !(linux || darwin) || !(amd64 || arm64) || sqlite3_flock || sqlite3_noshm || sqlite3_nosys
//go:build !(darwin || linux || illumos) || !(amd64 || arm64 || riscv64) || sqlite3_flock || sqlite3_noshm || sqlite3_nosys
package vfs