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)
MIGRATION_FILE_PATTERN | = | /\A\d+_.+\.rb\z/.freeze |
Migrates the supplied database in the specified directory from the current version to the target version. If no current version is supplied, it is extracted from a schema_info table. The schema_info table is automatically created and maintained by the apply function.
# File lib/sequel/extensions/migration.rb, line 136 136: def self.apply(db, directory, target = nil, current = nil) 137: # determine current and target version and direction 138: current ||= get_current_migration_version(db) 139: target ||= latest_migration_version(directory) 140: raise Error, "No current version available" if current.nil? 141: raise Error, "No target version available" if target.nil? 142: 143: direction = current < target ? :up : :down 144: 145: classes = migration_classes(directory, target, current, direction) 146: 147: db.transaction do 148: classes.each {|c| c.apply(db, direction)} 149: set_current_migration_version(db, target) 150: end 151: 152: target 153: end
Gets the current migration version stored in the database. If no version number is stored, 0 is returned.
# File lib/sequel/extensions/migration.rb, line 157 157: def self.get_current_migration_version(db) 158: r = schema_info_dataset(db).first 159: r ? r[:version] : 0 160: end
Returns the latest version available in the specified directory.
# File lib/sequel/extensions/migration.rb, line 163 163: def self.latest_migration_version(directory) 164: l = migration_files(directory).last 165: l ? File.basename(l).to_i : nil 166: end
Returns a list of migration classes filtered for the migration range and ordered according to the migration direction.
# File lib/sequel/extensions/migration.rb, line 170 170: def self.migration_classes(directory, target, current, direction) 171: range = direction == :up ? 172: (current + 1)..target : (target + 1)..current 173: 174: # Remove class definitions 175: Migration.descendants.each do |c| 176: Object.send(:remove_const, c.to_s) rescue nil 177: end 178: Migration.descendants.clear # remove any defined migration classes 179: 180: # load migration files 181: migration_files(directory, range).each {|fn| load(fn)} 182: 183: # get migration classes 184: classes = Migration.descendants 185: classes.reverse! if direction == :down 186: classes 187: end
Returns any found migration files in the supplied directory.
# File lib/sequel/extensions/migration.rb, line 190 190: def self.migration_files(directory, range = nil) 191: files = [] 192: Dir.new(directory).each do |file| 193: files[file.to_i] = File.join(directory, file) if MIGRATION_FILE_PATTERN.match(file) 194: end 195: filtered = range ? files[range] : files 196: filtered ? filtered.compact : [] 197: end
Returns the dataset for the schema_info table. If no such table exists, it is automatically created.
# File lib/sequel/extensions/migration.rb, line 201 201: def self.schema_info_dataset(db) 202: db.create_table(:schema_info) {integer :version} unless db.table_exists?(:schema_info) 203: db[:schema_info] 204: end