memdb

README

Go memdb SQLite VFS

This package implements the "memdb" SQLite VFS in pure Go.

It has some benefits over the C version:

• the memory backing the database needs not be contiguous,
• the database can grow/shrink incrementally without copying,
• reader-writer concurrency is slightly improved.

Documentation

Overview

Package memdb implements the "memdb" SQLite VFS.

The "memdb" vfs.VFS allows the same in-memory database to be shared among multiple database connections in the same process, as long as the database name begins with "/".

Importing package memdb registers the VFS:

import _ "github.com/ncruces/go-sqlite3/vfs/memdb"

Example

package main

import (
	"database/sql"
	"fmt"
	"log"

	_ "embed"

	_ "github.com/ncruces/go-sqlite3/driver"
	_ "github.com/ncruces/go-sqlite3/embed"
	"github.com/ncruces/go-sqlite3/vfs/memdb"
)

//go:embed testdata/test.db
var testDB []byte

func main() {
	memdb.Create("test.db", testDB)

	db, err := sql.Open("sqlite3", "file:/test.db?vfs=memdb")
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	_, err = db.Exec(`INSERT INTO users (id, name) VALUES (3, 'rust')`)
	if err != nil {
		log.Fatal(err)
	}

	rows, err := db.Query(`SELECT id, name FROM users`)
	if err != nil {
		log.Fatal(err)
	}
	defer rows.Close()

	for rows.Next() {
		var id, name string
		err = rows.Scan(&id, &name)
		if err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%s %s\n", id, name)
	}
}

Output:

0 go
1 zig
2 whatever
3 rust

Index

• func Delete(name string)
• func TestDB(tb testing.TB, params ...url.Values) string
• type MemDB
  • func Create(name string, data []byte) *MemDB
  • func (m *MemDB) Dump() io.ReadSeekCloser
• type MemDBDumper
  • func (m *MemDBDumper) Close() error
  • func (m *MemDBDumper) Read(p []byte) (n int, err error)
  • func (m *MemDBDumper) Seek(offset int64, whence int) (int64, error)

Examples

• Package

Functions

func Delete

func Delete(name string)

Delete deletes a shared memory database.

func TestDB

func TestDB(tb testing.TB, params ...url.Values) string

TestDB creates an empty shared memory database for the test to use. The database is automatically deleted when the test and all its subtests complete. Each subsequent call to TestDB returns a unique database.

Types

type MemDB

type MemDB struct {
	// contains filtered or unexported fields
}

MemDB is a no-export memDB struct dump helper. Note: This struct does not provide concurrency safety, and you must manage concurrent access yourself.

func Create

func Create(name string, data []byte) *MemDB

Create creates a shared memory database, using data as its initial contents. The new database takes ownership of data, and the caller should not use data after this call.

func (*MemDB) Dump

func (m *MemDB) Dump() io.ReadSeekCloser

type MemDBDumper

type MemDBDumper struct {
	// contains filtered or unexported fields
}

func (*MemDBDumper) Close

func (m *MemDBDumper) Close() error

func (*MemDBDumper) Read

func (m *MemDBDumper) Read(p []byte) (n int, err error)

func (*MemDBDumper) Seek

func (m *MemDBDumper) Seek(offset int64, whence int) (int64, error)