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107 lines
5.3 KiB
Markdown
107 lines
5.3 KiB
Markdown
# Go bindings to SQLite using Wazero
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[](https://pkg.go.dev/github.com/ncruces/go-sqlite3)
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[](https://goreportcard.com/report/github.com/ncruces/go-sqlite3)
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[](https://github.com/ncruces/go-sqlite3/wiki/Test-coverage-report)
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Go module `github.com/ncruces/go-sqlite3` wraps a [WASM](https://webassembly.org/) build of [SQLite](https://sqlite.org/),
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and uses [wazero](https://wazero.io/) to provide `cgo`-free SQLite bindings.
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- Package [`github.com/ncruces/go-sqlite3`](https://pkg.go.dev/github.com/ncruces/go-sqlite3)
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wraps the [C SQLite API](https://www.sqlite.org/cintro.html)
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([example usage](https://pkg.go.dev/github.com/ncruces/go-sqlite3#example-package)).
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- Package [`github.com/ncruces/go-sqlite3/driver`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/driver)
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provides a [`database/sql`](https://pkg.go.dev/database/sql) driver
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([example usage](https://pkg.go.dev/github.com/ncruces/go-sqlite3/driver#example-package)).
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- Package [`github.com/ncruces/go-sqlite3/embed`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/embed)
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embeds a build of SQLite into your application.
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- Package [`github.com/ncruces/go-sqlite3/vfs`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/vfs)
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wraps the [C SQLite VFS API](https://www.sqlite.org/vfs.html) and provides a pure Go implementation.
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- Package [`github.com/ncruces/go-sqlite3/vfs/memdb`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/vfs/memdb)
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implements an in-memory VFS.
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- Package [`github.com/ncruces/go-sqlite3/vfs/readervfs`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/vfs/readervfs)
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implements a VFS for immutable databases.
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- Package [`github.com/ncruces/go-sqlite3/ext/unicode`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/unicode)
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registers Unicode aware functions.
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- Package [`github.com/ncruces/go-sqlite3/ext/stats`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/ext/stats)
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registers [statistics functions](https://www.oreilly.com/library/view/sql-in-a/9780596155322/ch04s02.html).
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- Package [`github.com/ncruces/go-sqlite3/gormlite`](https://pkg.go.dev/github.com/ncruces/go-sqlite3/gormlite)
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provides a [GORM](https://gorm.io) driver.
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### Caveats
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This module replaces the SQLite [OS Interface](https://www.sqlite.org/vfs.html)
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(aka VFS) with a [pure Go](vfs/) implementation.
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This has benefits, but also comes with some drawbacks.
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#### Write-Ahead Logging
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Because WASM does not support shared memory,
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[WAL](https://www.sqlite.org/wal.html) support is [limited](https://www.sqlite.org/wal.html#noshm).
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To work around this limitation, SQLite is [patched](sqlite3/locking_mode.patch)
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to always use `EXCLUSIVE` locking mode for WAL databases.
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Because connection pooling is incompatible with `EXCLUSIVE` locking mode,
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to use the [`database/sql`](https://pkg.go.dev/database/sql)
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driver with WAL databases you should disable connection pooling by calling
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[`db.SetMaxOpenConns(1)`](https://pkg.go.dev/database/sql#DB.SetMaxOpenConns).
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#### POSIX Advisory Locks
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POSIX advisory locks, which SQLite uses, are
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[broken by design](https://www.sqlite.org/src/artifact/90c4fa?ln=1073-1161).
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On Linux, macOS and illumos, this module uses
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[OFD locks](https://www.gnu.org/software/libc/manual/html_node/Open-File-Description-Locks.html)
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to synchronize access to database files.
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OFD locks are fully compatible with process-associated POSIX advisory locks.
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On BSD Unixes, this module uses
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[BSD locks](https://man.freebsd.org/cgi/man.cgi?query=flock&sektion=2).
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BSD locks may _not_ be compatible with process-associated POSIX advisory locks
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(they are on FreeBSD).
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##### TL;DR
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In all platforms for which this package builds,
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it is safe to use it to access databases concurrently from multiple goroutines.
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Additionally, on Windows, Linux, macOS, illumos and FreeBSD,
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it is _also_ safe to use it to access databases concurrently
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with _other_ implementations of SQLite.
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On other BSDs, where this might be unsafe,
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[this test](https://github.com/ncruces/go-sqlite3/blob/main/vfs/lock_test.go) should fail.
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#### Testing
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The pure Go VFS is tested by running SQLite's
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[mptest](https://github.com/sqlite/sqlite/blob/master/mptest/mptest.c)
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on Linux, macOS and Windows;
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BSD code paths are tested on macOS using the `sqlite3_bsd` build tag.
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Performance is tested by running
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[speedtest1](https://github.com/sqlite/sqlite/blob/master/test/speedtest1.c).
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### Roadmap
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- [ ] advanced SQLite features
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- [x] custom functions
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- [x] nested transactions
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- [x] incremental BLOB I/O
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- [x] online backup
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- [ ] session extension
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- [ ] custom VFSes
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- [x] custom VFS API
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- [x] in-memory VFS
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- [x] read-only VFS, wrapping an [`io.ReaderAt`](https://pkg.go.dev/io#ReaderAt)
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- [ ] cloud-based VFS, based on [Cloud Backed SQLite](https://sqlite.org/cloudsqlite/doc/trunk/www/index.wiki)
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- [ ] [MVCC](https://en.wikipedia.org/wiki/Multiversion_concurrency_control) VFS, using [BadgerDB](https://github.com/dgraph-io/badger)
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### Alternatives
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- [`modernc.org/sqlite`](https://pkg.go.dev/modernc.org/sqlite)
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- [`crawshaw.io/sqlite`](https://pkg.go.dev/crawshaw.io/sqlite)
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- [`github.com/mattn/go-sqlite3`](https://pkg.go.dev/github.com/mattn/go-sqlite3)
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- [`github.com/zombiezen/go-sqlite`](https://pkg.go.dev/github.com/zombiezen/go-sqlite)
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