Class | Sequel::Migration
In: | lib/sequel/extensions/migration.rb
Parent: | Object

The Migration class describes a database migration that can be reversed. The migration looks very similar to ActiveRecord (Rails) migrations, e.g.:

      class CreateSessions < Sequel::Migration
        def up
          create_table :sessions do
            primary_key :id
            String :session_id, :size => 32, :unique => true
            DateTime :created_at
            text :data
          end
        end

        def down
          # You can use raw SQL if you need to
          self << 'DROP TABLE sessions'
        end
      end

      class AlterItems < Sequel::Migration
        def up
          alter_table :items do
            add_column :category, String, :default => 'ruby'
          end
        end

        def down
          alter_table :items do
            drop_column :category
          end
        end
      end

To apply a migration to a database, you can invoke the apply with the target database instance and the direction :up or :down, e.g.:

      DB = Sequel.connect('sqlite://mydb')
      CreateSessions.apply(DB, :up)

See Sequel::Schema::Generator for the syntax to use for creating tables, and Sequel::Schema::AlterTableGenerator for the syntax to use when altering existing tables. Migrations act as a proxy for the database given in apply, so inside down and up, you can act as though self refers to the database. So you can use any of the Sequel::Database instance methods directly.

### Methods

apply descendants down inherited method_missing new up

### Public Class methods

apply(db, direction)

Applies the migration to the supplied database in the specified direction.

[Source]

        # File lib/sequel/extensions/migration.rb, line 59
    59:     def self.apply(db, direction)
    60:       obj = new(db)
    61:       case direction
    62:       when :up
    63:         obj.up
    64:       when :down
    65:         obj.down
    66:       else
    67:         raise ArgumentError, "Invalid migration direction specified (#{direction.inspect})"
    68:       end
    69:     end

descendants()

Returns the list of Migration descendants.

[Source]

        # File lib/sequel/extensions/migration.rb, line 72
    72:     def self.descendants
    73:       @descendants ||= []
    74:     end

inherited(base)

Adds the new migration class to the list of Migration descendants.

[Source]

        # File lib/sequel/extensions/migration.rb, line 77
    77:     def self.inherited(base)
    78:       descendants << base
    79:     end

new(db)

Creates a new instance of the migration and sets the @db attribute.

[Source]

        # File lib/sequel/extensions/migration.rb, line 53
    53:     def initialize(db)
    54:       @db = db
    55:     end

### Public Instance methods

down()

The default down action does nothing

[Source]

        # File lib/sequel/extensions/migration.rb, line 82
    82:     def down
    83:     end

method_missing(method_sym, *args, &block)

Intercepts method calls intended for the database and sends them along.

[Source]

        # File lib/sequel/extensions/migration.rb, line 86
    86:     def method_missing(method_sym, *args, &block)
    87:       @db.send(method_sym, *args, &block)
    88:     end

up()

The default up action does nothing

[Source]

        # File lib/sequel/extensions/migration.rb, line 91
    91:     def up
    92:     end

[Validate]