Class | Sequel::Migrator
In: | lib/sequel/extensions/migration.rb
Parent: | Object

The `Migrator` class performs migrations based on migration files in a specified directory. The migration files should be named using the following pattern:

      <version>_<title>.rb

For example, the following files are considered migration files:

      001_create_sessions.rb
      002_add_data_column.rb

You can also use timestamps as version numbers:

      1273253850_create_sessions.rb
      1273257248_add_data_column.rb

If any migration filenames use timestamps as version numbers, Sequel uses the `TimestampMigrator` to migrate, otherwise it uses the `IntegerMigrator`. The `TimestampMigrator` can handle migrations that are run out of order as well as migrations with the same timestamp, while the `IntegerMigrator` is more strict and raises exceptions for missing or duplicate migration files.

The migration files should contain either one `Migration` subclass or one `Sequel.migration` call.

Migrations are generally run via the sequel command line tool, using the -m and -M switches. The -m switch specifies the migration directory, and the -M switch specifies the version to which to migrate.

You can apply migrations using the Migrator API, as well (this is necessary if you want to specify the version from which to migrate in addition to the version to which to migrate). To apply a migrator, the `apply` method must be invoked with the database instance, the directory of migration files and the target version. If no current version is supplied, it is read from the database. The migrator automatically creates a table (schema_info for integer migrations and schema_migrations for timestamped migrations). in the database to keep track of the current migration version. If no migration version is stored in the database, the version is considered to be 0. If no target version is specified, the database is migrated to the latest version available in the migration directory.

For example, to migrate the database to the latest version:

      Sequel::Migrator.apply(DB, '.')

For example, to migrate the database all the way down:

      Sequel::Migrator.apply(DB, '.', 0)

For example, to migrate the database to version 4:

      Sequel::Migrator.apply(DB, '.', 4)

To migrate the database from version 1 to version 5:

      Sequel::Migrator.apply(DB, '.', 5, 1)

Part of the `migration` extension.

### Methods

apply new run

### Classes and Modules

Class Sequel::Migrator::Error

### Constants

MIGRATION_FILE_PATTERN | = | /\A\d+_.+\.rb\z/i.freeze
MIGRATION_SPLITTER | = | '_'.freeze
MINIMUM_TIMESTAMP | = | 20000101

### Attributes

column | [R] | The column to use to hold the migration version number for integer migrations or filename for timestamp migrations (defaults to :version for integer migrations and :filename for timestamp migrations)
db | [R] | The database related to this migrator
directory | [R] | The directory for this migrator‘s files
ds | [R] | The dataset for this migrator, representing the `schema_info` table for integer migrations and the `schema_migrations` table for timestamp migrations
files | [R] | All migration files in this migrator‘s directory
table | [R] | The table to use to hold the applied migration data (defaults to :schema_info for integer migrations and :schema_migrations for timestamp migrations)
target | [R] | The target version for this migrator

### Public Class methods

apply(db, directory, target = nil, current = nil)

Wrapper for `run`, maintaining backwards API compatibility

[Source]

         # File lib/sequel/extensions/migration.rb, line 199
    199:     def self.apply(db, directory, target = nil, current = nil)
    200:       run(db, directory, :target => target, :current => current)
    201:     end

new(db, directory, opts={})

Setup the state for the migrator

[Source]

         # File lib/sequel/extensions/migration.rb, line 257
    257:     def initialize(db, directory, opts={})
    258:       raise(Error, "Must supply a valid migration path") unless File.directory?(directory)
    259:       @db = db
    260:       @directory = directory
    261:       @files = get_migration_files
    262:       @table = opts[:table]  || self.class.const_get(:DEFAULT_SCHEMA_TABLE)
    263:       @column = opts[:column] || self.class.const_get(:DEFAULT_SCHEMA_COLUMN)
    264:       @ds = schema_dataset
    265:     end

run(db, directory, opts={})

Migrates the supplied database using the migration files in the the specified directory. Options:

- :column :: The column in the :table argument storing the migration version (default: :version).
- :current :: The current version of the database. If not given, it is retrieved from the database

                  using the :table and :column options.

- :table :: The table containing the schema version (default: :schema_info).
- :target :: The target version to which to migrate. If not given, migrates to the maximum version.

Examples:

      Sequel::Migrator.run(DB, "migrations")
      Sequel::Migrator.run(DB, "migrations", :target=>15, :current=>10)
      Sequel::Migrator.run(DB, "app1/migrations", :column=> :app2_version)
      Sequel::Migrator.run(DB, "app2/migrations", :column => :app2_version, :table=>:schema_info2)

[Source]

         # File lib/sequel/extensions/migration.rb, line 215
    215:     def self.run(db, directory, opts={})
    216:       migrator_class(directory).new(db, directory, opts).run
    217:     end

[Validate]