class Sequel::Migrator
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.
Constants
- MIGRATION_FILE_PATTERN
- MIGRATION_SPLITTER
- MINIMUM_TIMESTAMP
Attributes
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)
The database related to this migrator
The directory for this migrator's files
The dataset for this migrator, representing the schema_info
table for integer migrations and the schema_migrations
table
for timestamp migrations
All migration files in this migrator's directory
The table to use to hold the applied migration data (defaults to :schema_info for integer migrations and :schema_migrations for timestamp migrations)
The target version for this migrator
Public Class Methods
Wrapper for run
, maintaining backwards API compatibility
# File lib/sequel/extensions/migration.rb, line 361 def self.apply(db, directory, target = nil, current = nil) run(db, directory, :target => target, :current => current) end
Raise a NotCurrentError unless the migrator is current, takes the same arguments as run.
# File lib/sequel/extensions/migration.rb, line 367 def self.check_current(*args) raise(NotCurrentError, 'migrator is not current') unless is_current?(*args) end
Return whether the migrator is current (i.e. it does not need to make any changes). Takes the same arguments as run.
# File lib/sequel/extensions/migration.rb, line 373 def self.is_current?(db, directory, opts=OPTS) migrator_class(directory).new(db, directory, opts).is_current? end
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.
# File lib/sequel/extensions/migration.rb, line 397 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
Setup the state for the migrator
# File lib/sequel/extensions/migration.rb, line 435 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
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)
# File lib/sequel/extensions/migration.rb, line 390 def self.run(db, directory, opts=OPTS) migrator_class(directory).new(db, directory, opts).run end
Private Instance Methods
If transactions should be used for the migration, yield to the block inside a transaction. Otherwise, just yield to the block.
# File lib/sequel/extensions/migration.rb, line 452 def checked_transaction(migration, &block) use_trans = if @use_transactions.nil? if migration.use_transactions.nil? @db.supports_transactional_ddl? else migration.use_transactions end else @use_transactions end if use_trans db.transaction(&block) else yield end end
Return the integer migration version based on the filename.
# File lib/sequel/extensions/migration.rb, line 481 def migration_version_from_file(filename) filename.split(MIGRATION_SPLITTER, 2).first.to_i end
Remove all migration classes. Done by the migrator to ensure that the correct migration classes are picked up.
# File lib/sequel/extensions/migration.rb, line 472 def remove_migration_classes # Remove class definitions Migration.descendants.each do |c| Object.send(:remove_const, c.to_s) rescue nil end Migration.descendants.clear # remove any defined migration classes end