To install the library and command line program, use the following:
go get github.com/rubenv/sql-migrate/...
$ sql-migrate --help usage: sql-migrate [--version] [--help] <command> [<args>] Available commands are: down Undo a database migration redo Reapply the last migration status Show migration status up Migrates the database to the most recent version available
Each command requires a configuration file (which defaults to dbconfig.yml
, but can be specified with the -config
flag). This config file should specify one or more environments:
development: dialect: sqlite3 datasource: test.db dir: migrations/sqlite3 production: dialect: postgres datasource: dbname=myapp sslmode=disable dir: migrations/postgres table: migrations
The table
setting is optional and will default to gorp_migrations
.
The environment that will be used can be specified with the -env
flag (defaults to development
).
Use the --help
flag in combination with any of the commands to get an overview of its usage:
$ sql-migrate up --help Usage: sql-migrate up [options] ... Migrates the database to the most recent version available. Options: -config=config.yml Configuration file to use. -env="development" Environment. -limit=0 Limit the number of migrations (0 = unlimited). -dryrun Don't apply migrations, just print them.
The up
command applies all available migrations. By contrast, down
will only apply one migration by default. This behavior can be changed for both by using the -limit
parameter.
The redo
command will unapply the last migration and reapply it. This is useful during development, when you're writing migrations.
Use the status
command to see the state of the applied migrations:
$ sql-migrate status +---------------+-----------------------------------------+ | MIGRATION | APPLIED | +---------------+-----------------------------------------+ | 1_initial.sql | 2014-09-13 08:19:06.788354925 +0000 UTC | | 2_record.sql | no | +---------------+-----------------------------------------+
Import sql-migrate into your application:
import "github.com/rubenv/sql-migrate"
Set up a source of migrations, this can be from memory, from a set of files or from bindata (more on that later):
// Hardcoded strings in memory: migrations := &migrate.MemoryMigrationSource{ Migrations: []*migrate.Migration{ &migrate.Migration{ Id: "123", Up: []string{"CREATE TABLE people (id int)"}, Down: []string{"DROP TABLE people"}, }, }, } // OR: Read migrations from a folder: migrations := &migrate.FileMigrationSource{ Dir: "db/migrations", } // OR: Use migrations from bindata: migrations := &migrate.AssetMigrationSource{ Asset: Asset, AssetDir: AssetDir, Dir: "migrations", }
Then use the Exec
function to upgrade your database:
db, err := sql.Open("sqlite3", filename) if err != nil { // Handle errors! } n, err := migrate.Exec(db, "sqlite3", migrations, migrate.Up) if err != nil { // Handle errors! } fmt.Printf("Applied %d migrations!\n", n)
Note that n
can be greater than 0
even if there is an error: any migration that succeeded will remain applied even if a later one fails.
Check the GoDoc reference for the full documentation.
Migrations are defined in SQL files, which contain a set of SQL statements. Special comments are used to distinguish up and down migrations.
-- +migrate Up -- SQL in section 'Up' is executed when this migration is applied CREATE TABLE people (id int); -- +migrate Down -- SQL section 'Down' is executed when this migration is rolled back DROP TABLE people;
You can put multiple statements in each block, as long as you end them with a semicolon (;
).
If you have complex statements which contain semicolons, use StatementBegin
and StatementEnd
to indicate boundaries:
-- +migrate Up CREATE TABLE people (id int); -- +migrate StatementBegin CREATE OR REPLACE FUNCTION do_something() returns void AS $$ DECLARE create_query text; BEGIN -- Do something here END; $$ language plpgsql; -- +migrate StatementEnd -- +migrate Down DROP FUNCTION do_something(); DROP TABLE people;
The order in which migrations are applied is defined through the filename: sql-migrate will sort migrations based on their name. It's recommended to use an increasing version number or a timestamp as the first part of the filename.
If you like your Go applications self-contained (that is: a single binary): use bindata to embed the migration files.
Just write your migration files as usual, as a set of SQL files in a folder.
Then use bindata to generate a .go
file with the migrations embedded:
go-bindata -pkg myapp -o bindata.go db/migrations/
The resulting bindata.go
file will contain your migrations. Remember to regenerate your bindata.go
file whenever you add/modify a migration (go generate
will help here, once it arrives).
Use the AssetMigrationSource
in your application to find the migrations:
migrations := &migrate.AssetMigrationSource{
Asset: Asset,
AssetDir: AssetDir,
Dir: "db/migrations",
}
Both Asset
and AssetDir
are functions provided by bindata.
Then proceed as usual.
Adding a new migration source means implementing MigrationSource
.
type MigrationSource interface {
FindMigrations() ([]*Migration, error)
}
The resulting slice of migrations will be executed in the given order, so it should usually be sorted by the Id
field.
(The MIT License) Copyright (C) 2014 by Ruben Vermeersch <ruben@rocketeer.be> Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.