github.com/alicebob/sqlittle

Package SQLittle provides pure Go, read-only, access to SQLite (version 3) database files.

What

SQLittle reads SQLite3 tables and indexes. It iterates over tables, and can search efficiently using indexes. SQLittle will deal with all SQLite storage quirks, but otherwise it doesn't try to be smart; if you want to use an index you have to give the name of the index.

There is no support for SQL, and if you want to do the most efficient joins possible you'll have to use the low level code.

Based on https://sqlite.org/fileformat2.html and some SQLite source code reading.

Why

This whole thing is mostly for fun. The normal SQLite libraries are perfectly great, and there is no real need for this. However, since this library is pure Go cross-compilation is much easier. Given the constraints a valid use-case would for example be storing app configuration in read-only sqlite files.

Docs

https://godoc.org/github.com/alicebob/sqlittle for the go doc and examples.

See LOWLEVEL.md about the low level reader. See CODE.md for an overview how the code is structured.

Features

Things SQLittle can do:

- table scan in row order; table scan in index order; simple searches with use of (partial) indexes
- works on both rowid and non-rowid (`WITHOUT ROWID`) tables
- files can be used concurrently with sqlite (compatible locks)
- behaves nicely on corrupted database files (no panics)
- detects corrupt journal files
- hides all SQLite low level storage details
- DESC indexes are handled automatically
- Collate functions are used automatically
- indexes with expression (either in columns or as a `WHERE`) are (partially) supported
- Scan() to most Go datatypes, including `time.Time`
- works on Linux, Mac OS, and Windows
- has an experimental database/sql driver, see below

Things SQLittle should do:

- add a helper to find indexes. That would be especially useful for the `sqlite_autoindex_...` indexes
- optimize loading when all requested columns are available in the index
- expose the locking so you can do bigger read transactions

Things SQLittle can not do:

- read-only
- only supports UTF8 strings
- no joins
- WAL files are not supported
- indexes are used for sorting, but there is no on-the-fly sorting

Locks

SQLittle has a read-lock on the file during the whole execution of the select-like functions. It's safe to update the database using SQLite while the file is opened in SQLittle.

Status

The current level of abstraction is likely the final one (that is: deal with reading single tables; don't even try joins or SQL or query planning), but the API might still change.

Examples

Basic SELECT

Code:

{
	db, err := sqlittle.Open("./testdata/music.sqlite")
	if err != nil {
		panic(err)
	}
	defer db.Close()
	db.Select("tracks", func(r sqlittle.Row) {
		var (
			name   string
			length int
		)
		_ = r.Scan(&name, &length)
		fmt.Printf("%s: %d seconds\n", name, length)
	}, "name", "length")
}

Output:

Drive My Car: 145 seconds
Norwegian Wood: 121 seconds
You Wont See Me: 198 seconds
Come Together: 259 seconds
Something: 182 seconds
Maxwells Silver Hammer: 207 seconds

SELECT by primary key

Code:

{
	db, err := sqlittle.Open("./testdata/music.sqlite")
	if err != nil {
		panic(err)
	}
	defer db.Close()
	db.PKSelect("tracks", sqlittle.Key{4}, func(r sqlittle.Row) {
		name, _ := r.ScanString()
		fmt.Printf("%s\n", name)
	}, "name")
}

Output:

Come Together

Driver

The ./driver/ package implements an experimental driver for database/sql. It currently supports very basic SELECT statements only. Issues, PRs, and feature requests are (as always) welcome.

Idea

The driver exposes sqlittle as a database/sql driver. It uses the main sqlittle package to implement a basic query executor, which can be used as any other Go database driver.

It will never support full SQL, but certain things we can do without implementing an actual database system. For example ORDER BY could be supported, as long as you have an index which we can use for it. LIMIT should be easy. But GROUP BY needs an actual database system, so that's out.

Supported SQL

These statements are supported. Anything else is not:

• SELECT * FROM yourtable
• SELECT col1, col2 FROM yourtable

example

import (
	"database/sql"

	_ "github.com/alicebob/sqlittle/driver"
)

func Albums() {
	c, err := sql.Open("sqlittle", "../testdata/music.sqlite")
	rows, err := c.Query(`SELECT * FROM albums`)
	// normal rows.Next() stuff
	// Be sure to check rows.Err()!
}

&c.

make fuzz uses go-fuzz

See sqlite2go for another approach to pure Go SQLite