Module Sequel::Migrator
In: lib/sequel/extensions/migration.rb

The Migrator module performs migrations based on migration files in a specified directory. The migration files should be named using the following pattern (in similar fashion to ActiveRecord migrations):

  <version>_<title>.rb

For example, the following files are considered migration files:

  001_create_sessions.rb
  002_add_data_column.rb
  ...

The migration files should contain one or more migration classes based on Sequel::Migration.

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 migration, 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 schema_info table 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, '.')

To migrate the database from version 1 to version 5:

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

Methods

Constants

DEFAULT_SCHEMA_COLUMN = :version
DEFAULT_SCHEMA_TABLE = :schema_info
MIGRATION_FILE_PATTERN = /\A\d+_.+\.rb\z/.freeze
MIGRATION_SPLITTER = '_'.freeze

Public Class methods

Wrapper for run, maintaining backwards API compatibility

[Source]

     # File lib/sequel/extensions/migration.rb, line 140
140:     def self.apply(db, directory, target = nil, current = nil)
141:       run(db, directory, :target => target, :current => current)
142:     end

Gets the current migration version stored in the database. If no version number is stored, 0 is returned.

[Source]

     # File lib/sequel/extensions/migration.rb, line 175
175:     def self.get_current_migration_version(db, opts={})
176:       (schema_info_dataset(db, opts).first || {})[opts[:column] || DEFAULT_SCHEMA_COLUMN] || 0
177:     end

Returns the latest version available in the specified directory.

[Source]

     # File lib/sequel/extensions/migration.rb, line 180
180:     def self.latest_migration_version(directory)
181:       l = migration_files(directory).last
182:       l ? migration_version_from_file(File.basename(l)) : nil
183:     end

Returns a list of migration classes filtered for the migration range and ordered according to the migration direction.

[Source]

     # File lib/sequel/extensions/migration.rb, line 187
187:     def self.migration_classes(directory, target, current, direction)
188:       range = direction == :up ?
189:         (current + 1)..target : (target + 1)..current
190: 
191:       # Remove class definitions
192:       Migration.descendants.each do |c|
193:         Object.send(:remove_const, c.to_s) rescue nil
194:       end
195:       Migration.descendants.clear # remove any defined migration classes
196: 
197:       # load migration files
198:       migration_files(directory, range).each {|fn| load(fn)}
199:       
200:       # get migration classes
201:       classes = Migration.descendants
202:       classes.reverse! if direction == :down
203:       classes
204:     end

Returns any found migration files in the supplied directory.

[Source]

     # File lib/sequel/extensions/migration.rb, line 207
207:     def self.migration_files(directory, range = nil)
208:       files = []
209:       Dir.new(directory).each do |file|
210:         files[migration_version_from_file(file)] = File.join(directory, file) if MIGRATION_FILE_PATTERN.match(file)
211:       end
212:       filtered = range ? files[range] : files
213:       filtered ? filtered.compact : []
214:     end

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 156
156:     def self.run(db, directory, opts={})
157:       raise(Error, "Must supply a valid migration path") unless directory and File.directory?(directory)
158:       raise(Error, "No current version available") unless current = opts[:current] || get_current_migration_version(db, opts)
159:       raise(Error, "No target version available") unless target  = opts[:target]  || latest_migration_version(directory)
160: 
161:       direction = current < target ? :up : :down
162:       
163:       classes = migration_classes(directory, target, current, direction)
164: 
165:       db.transaction do
166:         classes.each {|c| c.apply(db, direction)}
167:         set_current_migration_version(db, target, opts)
168:       end
169:       
170:       target
171:     end

Returns the dataset for the schema_info table. If no such table exists, it is automatically created.

[Source]

     # File lib/sequel/extensions/migration.rb, line 218
218:     def self.schema_info_dataset(db, opts={})
219:       column = opts[:column] || DEFAULT_SCHEMA_COLUMN
220:       table  = opts[:table]  || DEFAULT_SCHEMA_TABLE
221:       db.create_table?(table){Integer column}
222:       db.alter_table(table){add_column column, Integer} unless db.from(table).columns.include?(column)
223:       db.from(table)
224:     end

Sets the current migration version stored in the database.

[Source]

     # File lib/sequel/extensions/migration.rb, line 227
227:     def self.set_current_migration_version(db, version, opts={})
228:       column = opts[:column] || DEFAULT_SCHEMA_COLUMN
229:       dataset = schema_info_dataset(db, opts)
230:       dataset.send(dataset.first ? :update : :insert, column => version)
231:     end

[Validate]