fathom/vendor/github.com/rubenv/sql-migrate

sql-migrate

SQL Schema migration tool for Go. Based on gorp and goose.

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 -v 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
    new       Create a new 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 new command creates a new empty migration template using the following pattern <current time>-<name>.sql.

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                                      |
+---------------+-----------------------------------------+

MySQL Caveat

If you are using MySQL, you must append ?parseTime=true to the datasource configuration. For example:

production:
    dialect: mysql
    datasource: root@/dbname?parseTime=true
    dir: migrations/mysql
    table: migrations

See here for more information.

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 a packr box
migrations := &migrate.PackrMigrationSource{
    Box: packr.NewBox("./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 (;).

You can alternatively set up a separator string that matches an entire line by setting sqlparse.LineSeparator. This can be used to imitate, for example, MS SQL Query Analyzer functionality where commands can be separated by a line with contents of GO. If sqlparse.LineSeparator is matched, it will not be included in the resulting migration scripts.

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.

Normally each migration is run within a transaction in order to guarantee that it is fully atomic. However some SQL commands (for example creating an index concurrently in PostgreSQL) cannot be executed inside a transaction. In order to execute such a command in a migration, the migration can be run using the notransaction option:

-- +migrate Up notransaction
CREATE UNIQUE INDEX people_unique_id_idx CONCURRENTLY ON people (id);

-- +migrate Down
DROP INDEX people_unique_id_idx;

Embedding migrations with packr

If you like your Go applications self-contained (that is: a single binary): use packr to embed the migration files.

Just write your migration files as usual, as a set of SQL files in a folder.

Use the PackrMigrationSource in your application to find the migrations:

migrations := &migrate.PackrMigrationSource{
    Box: packr.NewBox("./migrations"),
}

If you already have a box and would like to use a subdirectory:

migrations := &migrate.PackrMigrationSource{
    Box: myBox,
    Dir: "./migrations",
}

Embedding migrations with bindata

As an alternative, but slightly less maintained, you can 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

This library is distributed under the MIT license.