Class: Sequel::Migrator

Inherits:
Object show all
Defined in:
lib/sequel/extensions/migration.rb

Overview

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.

Direct Known Subclasses

IntegerMigrator, TimestampMigrator

Defined Under Namespace

Classes: Error, NotCurrentError

Constant Summary collapse

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

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(db, directory, opts = OPTS) ⇒ Migrator

Setup the state for the migrator

Raises:



434
435
436
437
438
439
440
441
442
443
444
445
 
# File 'lib/sequel/extensions/migration.rb', line 434

def initialize(db, directory, opts=OPTS)
  raise(Error, "Must supply a valid migration path") unless File.directory?(directory)
  @db = db
  @directory = directory
  @allow_missing_migration_files = opts[:allow_missing_migration_files]
  @files = get_migration_files
  schema, table = @db.send(:schema_and_table, opts[:table]  || self.class.const_get(:DEFAULT_SCHEMA_TABLE))
  @table = schema ? Sequel::SQL::QualifiedIdentifier.new(schema, table) : table
  @column = opts[:column] || self.class.const_get(:DEFAULT_SCHEMA_COLUMN)
  @ds = schema_dataset
  @use_transactions = opts[:use_transactions]
end

Instance Attribute Details

#column ⇒ Object (readonly)

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)



411
412
413
 
# File 'lib/sequel/extensions/migration.rb', line 411

def column
  @column
end

#db ⇒ Object (readonly)

The database related to this migrator



414
415
416
 
# File 'lib/sequel/extensions/migration.rb', line 414

def db
  @db
end

#directory ⇒ Object (readonly)

The directory for this migrator’s files



417
418
419
 
# File 'lib/sequel/extensions/migration.rb', line 417

def directory
  @directory
end

#ds ⇒ Object (readonly)

The dataset for this migrator, representing the schema_info table for integer migrations and the schema_migrations table for timestamp migrations



421
422
423
 
# File 'lib/sequel/extensions/migration.rb', line 421

def ds
  @ds
end

#files ⇒ Object (readonly)

All migration files in this migrator’s directory



424
425
426
 
# File 'lib/sequel/extensions/migration.rb', line 424

def files
  @files
end

#table ⇒ Object (readonly)

The table to use to hold the applied migration data (defaults to :schema_info for integer migrations and :schema_migrations for timestamp migrations)



428
429
430
 
# File 'lib/sequel/extensions/migration.rb', line 428

def table
  @table
end

#target ⇒ Object (readonly)

The target version for this migrator



431
432
433
 
# File 'lib/sequel/extensions/migration.rb', line 431

def target
  @target
end

Class Method Details

.apply(db, directory, target = nil, current = nil) ⇒ Object

Wrapper for run, maintaining backwards API compatibility



360
361
362
 
# File 'lib/sequel/extensions/migration.rb', line 360

def self.apply(db, directory, target = nil, current = nil)
  run(db, directory, :target => target, :current => current)
end

.check_current(*args) ⇒ Object

Raise a NotCurrentError unless the migrator is current, takes the same arguments as #run.

Raises:



366
367
368
 
# File 'lib/sequel/extensions/migration.rb', line 366

def self.check_current(*args)
  raise(NotCurrentError, 'migrator is not current') unless is_current?(*args)
end

.is_current?(db, directory, opts = OPTS) ⇒ Boolean

Return whether the migrator is current (i.e. it does not need to make any changes). Takes the same arguments as #run.

Returns:

  • (Boolean) 


372
373
374
 
# File 'lib/sequel/extensions/migration.rb', line 372

def self.is_current?(db, directory, opts=OPTS)
  migrator_class(directory).new(db, directory, opts).is_current?
end

.migrator_class(directory) ⇒ Object

Choose the Migrator subclass to use. Uses the TimestampMigrator if the version number appears to be a unix time integer for a year after 2005, otherwise uses the IntegerMigrator.



396
397
398
399
400
401
402
403
404
405
406
 
# File 'lib/sequel/extensions/migration.rb', line 396

def self.migrator_class(directory)
  if self.equal?(Migrator)
    Dir.new(directory).each do |file|
      next unless MIGRATION_FILE_PATTERN.match(file)
      return TimestampMigrator if file.split(MIGRATION_SPLITTER, 2).first.to_i > MINIMUM_TIMESTAMP
    end
    IntegerMigrator
  else
    self
  end
end

.run(db, directory, opts = OPTS) ⇒ Object

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

:allow_missing_migration_files

Don’t raise an error if there are missing migration files.

: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)



389
390
391
 
# File 'lib/sequel/extensions/migration.rb', line 389

def self.run(db, directory, opts=OPTS)
  migrator_class(directory).new(db, directory, opts).run
end