Class: Sequel::Migrator
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, or the target version specified is greater than the latest version available, 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.run(DB, '.')
For example, to migrate the database all the way down:
Sequel::Migrator.run(DB, '.', target: 0)
For example, to migrate the database to version 4:
Sequel::Migrator.run(DB, '.', target: 4)
To migrate the database from version 1 to version 5:
Sequel::Migrator.run(DB, '.', target: 5, current: 1)
Part of the migration
extension.
Direct Known Subclasses
Defined Under Namespace
Classes: Error, NotCurrentError
Constant Summary collapse
- MIGRATION_FILE_PATTERN =
/\A(\d+)_.+\.rb\z/i.freeze
- MUTEX =
Mutex used around migration file loading
Mutex.new
Instance Attribute Summary collapse
-
#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).
-
#db ⇒ Object
readonly
The database related to this migrator.
-
#directory ⇒ Object
readonly
The directory for this migrator's files.
-
#ds ⇒ Object
readonly
The dataset for this migrator, representing the
schema_info
table for integer migrations and theschema_migrations
table for timestamp migrations. -
#files ⇒ Object
readonly
All migration files in this migrator's directory.
-
#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).
-
#target ⇒ Object
readonly
The target version for this migrator.
Class Method Summary collapse
-
.apply(db, directory, target = nil, current = nil) ⇒ Object
Wrapper for
run
, maintaining backwards API compatibility. -
.check_current(*args) ⇒ Object
Raise a NotCurrentError unless the migrator is current, takes the same arguments as #run.
-
.is_current?(db, directory, opts = OPTS) ⇒ Boolean
Return whether the migrator is current (i.e. it does not need to make any changes).
-
.migrator_class(directory) ⇒ Object
Choose the Migrator subclass to use.
-
.run(db, directory, opts = OPTS) ⇒ Object
Migrates the supplied database using the migration files in the specified directory.
Instance Method Summary collapse
-
#initialize(db, directory, opts = OPTS) ⇒ Migrator
constructor
Setup the state for the migrator.
Constructor Details
#initialize(db, directory, opts = OPTS) ⇒ Migrator
Setup the state for the migrator
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# File 'lib/sequel/extensions/migration.rb', line 453 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] || default_schema_table) @table = schema ? Sequel::SQL::QualifiedIdentifier.new(schema, table) : table @column = opts[:column] || default_schema_column @ds = schema_dataset @use_transactions = opts[:use_transactions] 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 430 def column @column end |
#db ⇒ Object (readonly)
The database related to this migrator
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# File 'lib/sequel/extensions/migration.rb', line 433 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 436 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 440 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 443 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 447 def table @table end |
#target ⇒ Object (readonly)
The target version for this migrator
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# File 'lib/sequel/extensions/migration.rb', line 450 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 373 def self.apply(db, directory, target = nil, current = nil) run(db, directory, :target => target, :current => current) end |
.check_current(*args) ⇒ Object
Raise a NotCurrentError unless the migrator is current, takes the same arguments as #run.
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# File 'lib/sequel/extensions/migration.rb', line 379 def self.check_current(*args) raise(NotCurrentError, 'migrator is not current') unless is_current?(*args) end |
.is_current?(db, directory, opts = OPTS) ⇒ Boolean
Return whether the migrator is current (i.e. it does not need to make any changes). Takes the same arguments as #run.
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# File 'lib/sequel/extensions/migration.rb', line 385 def self.is_current?(db, directory, opts=OPTS) migrator_class(directory).new(db, directory, opts).is_current? end |
.migrator_class(directory) ⇒ Object
Choose the Migrator subclass to use. Uses the TimestampMigrator if the version number is greater than 20000101, otherwise uses the IntegerMigrator.
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# File 'lib/sequel/extensions/migration.rb', line 414 def self.migrator_class(directory) if self.equal?(Migrator) raise(Error, "Must supply a valid migration path") unless File.directory?(directory) Dir.new(directory).each do |file| next unless MIGRATION_FILE_PATTERN.match(file) return TimestampMigrator if file.split('_', 2).first.to_i > 20000101 end IntegerMigrator else self end end |
.run(db, directory, opts = OPTS) ⇒ Object
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. It is very risky to use this option, since it can result in the database schema version number not matching the expected database schema.
- :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.
- :relative
-
Run the given number of migrations, with a positive number being migrations to migrate up, and a negative number being migrations to migrate down (IntegerMigrator only).
- :table
-
The table containing the schema version (default: :schema_info for integer migrations and :schema_migrations for timestamped migrations).
- :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 408 def self.run(db, directory, opts=OPTS) migrator_class(directory).new(db, directory, opts).run end |