Module: Sequel::Migrator

Module | Sequel::Migrator
In: | lib/sequel_core/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

apply get_current_migration_version latest_migration_version migration_classes migration_files schema_info_dataset set_current_migration_version

### Constants

MIGRATION_FILE_PATTERN | = | /\A\d+_.+\.rb\z/.freeze

### Public Class methods

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

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.

[Source]

         # File lib/sequel_core/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

get_current_migration_version(db)

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

[Source]

         # File lib/sequel_core/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

latest_migration_version(directory)

Returns the latest version available in the specified directory.

[Source]

         # File lib/sequel_core/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

migration_classes(directory, target, current, direction)

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

[Source]

         # File lib/sequel_core/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

migration_files(directory, range = nil)

Returns any found migration files in the supplied directory.

[Source]

         # File lib/sequel_core/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

schema_info_dataset(db)

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

[Source]

         # File lib/sequel_core/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

set_current_migration_version(db, version)

Sets the current migration version stored in the database.

[Source]

         # File lib/sequel_core/migration.rb, line 207
    207:     def self.set_current_migration_version(db, version)
    208:       dataset = schema_info_dataset(db)
    209:       dataset.send(dataset.first ? :update : :<<, :version => version)
    210:     end

[Validate]