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

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 = {}) ⇒ Migrator

Setup the state for the migrator

Raises:



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# File 'lib/sequel/extensions/migration.rb', line 257

def initialize(db, directory, opts={})
  raise(Error, "Must supply a valid migration path") unless File.directory?(directory)
  @db = db
  @directory = directory
  @files = get_migration_files
  @table = opts[:table]  || self.class.const_get(:DEFAULT_SCHEMA_TABLE)
  @column = opts[:column] || self.class.const_get(:DEFAULT_SCHEMA_COLUMN)
  @ds = schema_dataset
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)



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# File 'lib/sequel/extensions/migration.rb', line 234

def column
  @column
end

#db ⇒ Object (readonly)

The database related to this migrator



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# File 'lib/sequel/extensions/migration.rb', line 237

def db
  @db
end

#directory ⇒ Object (readonly)

The directory for this migrator’s files



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# File 'lib/sequel/extensions/migration.rb', line 240

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



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# File 'lib/sequel/extensions/migration.rb', line 244

def ds
  @ds
end

#files ⇒ Object (readonly)

All migration files in this migrator’s directory



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# File 'lib/sequel/extensions/migration.rb', line 247

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)



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# File 'lib/sequel/extensions/migration.rb', line 251

def table
  @table
end

#target ⇒ Object (readonly)

The target version for this migrator



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# File 'lib/sequel/extensions/migration.rb', line 254

def target
  @target
end

Class Method Details

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

Wrapper for run, maintaining backwards API compatibility



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# File 'lib/sequel/extensions/migration.rb', line 199

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

.run(db, directory, opts = {}) ⇒ Object

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)



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# File 'lib/sequel/extensions/migration.rb', line 215

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