8 KiB
sql-migrate
Using modl? Check out modl-migrate.
Features
- Usable as a CLI tool or as a library
- Supports SQLite, PostgreSQL, MySQL, MSSQL and Oracle databases (through gorp)
- Can embed migrations into your application
- Migrations are defined with SQL for full flexibility
- Atomic migrations
- Up/down migrations to allow rollback
- Supports multiple database types in one project
Installation
To install the library and command line program, use the following:
go get github.com/rubenv/sql-migrate/...
Usage
As a standalone tool
$ 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 |
+---------------+-----------------------------------------+
As a library
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.
Writing migrations
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.
Embedding migrations with bindata
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.
Extending
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.
License
(The MIT License)
Copyright (C) 2014-2015 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.