gogo

Gogo handles database migrations in Go code like yoyo-migrate for python (well, a little like that).

It has been tested with MySQL, Postgresql and with SQLITE3 driver.

USAGE

gogo considers a migration to be a gogo.Migration struct:

type Migration struct {
	Apply    func(*Tx)
	Rollback func(*Tx)
}

In practice, you create an array like so:

var myMigrations = []*gogo.Migration{
	{
		Apply: func(tx *gogo.Tx) {

		},
		Rollback: func(tx *gogo.Tx) {

		},
	},
}

To migrate the database to the latest version, gogo has:

// Apply migrates the database to the latest migration version
func Migrate(db *sql.DB, migrations []Migration) (err error) {

In your code, you would use:

	err := gogo.Migrate(db, myMigrations)
	if nil!=err {
		log.Fatal(err)
	}

gogo will always migrate to the latest version (which it tracks in the database using a table called, _gogo_migrations, although you can rename it with the function gogo.MetaTable("gogo_version_table") for instance).

Rolling back a database is equally easy:

func Rollback(db *sql.DB, destinationVersionString string, migrations []Migration) (err error) {

In practice, this becomes:

	rollbackTo := flag.StringVar(`rollback`, `-1`, `rollback the database version to the nth-to-last migration`)
	flag.Parse()
	if ``!=*rollbackTo {
		err := gogo.Rollback(db, *rollbackTo, myMigrations)
		if nil!=err {
			log.Fatal(err)
		}
	}

When providing a rollback version, you can use a positive number (e.g. 0 would roll you right back to the database before any migrations were applied), or a negative number (-1 rolls back only the last migration defined, -2 the last 2 defined migrations), and so on. NOTE that the migration is calculated from the migrations defined, not the migrations applied. So if you -rollback -1 if will roll the database back to the next-to-last migration. If you -rollback -1 a second time, nothing will happen, because the database is already at the next-to-last migration.

DEFINING MIGRATION

The gogo.Migration methods Apply(tx *gogo.Tx) and Rollback(tx *gogo.Tx) come with an augemented *sql.Tx, that adds some utility functions. See the godoc or Tx.go for these.

FAILING MIGRATION

To fail a migration (or a rollback of one), just panic. gogo will catch the panic and report an error.

ERROR MESSAGES

Errors that occur while gogo executes are reported with gogo.PrintError. This is defined in the file Log.go as:

var PrintError = func(f string, args... interface{}) {
	fmt.Fprintf(os.Stderr, f, args...)
	log.Printf(f, args...)	
}

To use your own error logging, just set this to your own function:

	gogo.PrintError = func(f string, args... interface{}) {
		// ... handle the error yourself
	}

DIFFERENT DATABASES

gogo works with MySQL / Mariadb by default. However, it also supports Postgres and SQLite3.

To use a different database, you need to call gogo.SetInterface(gogo.DbInterface). gogo has three defined DbInterfaces: gogo.MysqlInterface, gogo.PgInterface and gogo.Sqlite3Interface. So, to use gogo with PostgresQL, you need:

gogo.SetInterface(&gogo.PgInterface)

To use gogo with Sqlite3:

gogo.SetInterface(&gogo.Sqlite3Interface)