goose

goose is a database migration tool.

You can manage your database's evolution by creating incremental SQL or Go scripts.

Install

$ go get bitbucket.org/liamstask/goose

This will install the goose binary to your $GOPATH/bin directory.

Usage

goose provides several commands to help manage your database schema.

create

Create a new migration script.

$ goose create AddSomeColumns
$ goose: created db/migrations/20130106093224_AddSomeColumns.go

Edit the newly created script to define the behavior of your migration.

up

Apply all available migrations.

$ goose up
$ goose: migrating db environment 'development', current version: 0, target: 3
$ OK    001_basics.sql
$ OK    002_next.sql
$ OK    003_and_again.go

down

Roll back a single migration from the current version.

$ goose down
$ goose: migrating db environment 'development', current version: 3, target: 2
$ OK    003_and_again.go

status

Print the status of all migrations:

$ goose status
$ goose: status for environment 'development'
$   Applied At                  Migration
$   =======================================
$   Sun Jan  6 11:25:03 2013 -- 001_basics.sql
$   Sun Jan  6 11:25:03 2013 -- 002_next.sql
$   Pending                  -- 003_and_again.go

goose -h provides more detailed info on each command.

Migrations

goose supports migrations written in SQL or in Go.

SQL Migrations

A sample SQL migration looks like:

:::sql
-- +goose Up
CREATE TABLE post (
    id int NOT NULL,
    title text,
    body text,
    PRIMARY KEY(id)
);

-- +goose Down
DROP TABLE post;

Notice the annotations in the comments. Any statements following -- +goose Up will be executed as part of a forward migration, and any statements following -- +goose Down will be executed as part of a rollback.

Go Migrations

A sample Go migration looks like:

:::go
package migration_003

import (
    "database/sql"
    "fmt"
)

func Up(txn *sql.Tx) {
    fmt.Println("Hello from migration_003 Up!")
}

func Down(txn *sql.Tx) {
    fmt.Println("Hello from migration_003 Down!")
}

Up() will be executed as part of a forward migration, and Down() will be executed as part of a rollback.

A transaction is provided, rather than the DB instance directly, since goose also needs to record the schema version within the same transaction. Each migration should run as a single transaction to ensure DB integrity, so it's good practice anyway.

Configuration

goose expects you to maintain a folder (typically called "db"), which contains the following:

• a dbconf.yml file that describes the database configurations you'd like to use
• a folder called "migrations" which contains .sql and/or .go scripts that implement your migrations

You may use the -path option to specify an alternate location for the folder containing your config and migrations.

A sample dbconf.yml looks like

development:
    driver: postgres
    open: user=liam dbname=tester sslmode=disable

Here, development specifies the name of the environment, and the driver and open elements are passed directly to database/sql to access the specified database.

You may include as many environments as you like, and you can use the -env command line option to specify which one to use. goose defaults to using an environment called development.

goose will expand environment variables in the open element. For an example, see the Heroku section below.

Other Drivers

goose knows about some common SQL drivers, but it can still be used to run Go-based migrations with any driver supported by database/sql. An import path and known dialect are required.

Currently, available dialects are: "postgres" or "mysql"

To run Go-based migrations with another driver, specify its import path and dialect, as shown below.

customdriver:
    driver: custom
    open: custom open string
    import: github.com/custom/driver
    dialect: mysql

NOTE: Because migrations written in SQL are executed directly by the goose binary, only drivers compiled into goose may be used for these migrations.

Using goose with Heroku

These instructions assume that you're using Keith Rarick's Heroku Go buildpack. First, add a file to your project called (e.g.) install_goose.go to trigger building of the goose executable during deployment, with these contents:

// use build constraints to work around http://code.google.com/p/go/issues/detail?id=4210
// +build heroku
package main

import _ "bitbucket.org/liamstask/goose"

Set up your Heroku database(s) as usual.

Then make use of environment variable expansion in your dbconf.yml:

production:
    driver: postgres
    open: $DATABASE_URL

To run goose in production, use heroku run:

heroku run goose -env production up