Module: DataMapper::MigrationRunner

Defined in:
lib/dm-migrations/migration_runner.rb

Instance Method Summary collapse

Instance Method Details

#migrate_down!(level = nil) ⇒ Object

Run all the down steps for the migrations that have already been run.

has an optional argument ‘level’ which, if supplied, only performs the down migrations with a postion greater than the level.



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# File 'lib/dm-migrations/migration_runner.rb', line 68

def migrate_down!(level = nil)
  migrations.sort.reverse.each do |migration|
    if level.nil?
      migration.perform_down()
    else
      migration.perform_down() if migration.position > level.to_i
    end
  end
end

#migrate_up!(level = nil) ⇒ Object

Run all migrations that need to be run. In most cases, this would be called by a rake task as part of a larger project, but this provides the ability to run them in a script or test.

has an optional argument ‘level’ which if supplied, only performs the migrations with a position less than or equal to the level.



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# File 'lib/dm-migrations/migration_runner.rb', line 54

def migrate_up!(level = nil)
  migrations.sort.each do |migration|
    if level.nil?
      migration.perform_up()
    else
      migration.perform_up() if migration.position <= level.to_i
    end
  end
end

#migration(number, name, opts = {}, &block) ⇒ Object

Creates a new migration, and adds it to the list of migrations to be run. Migrations can be defined in any order, they will be sorted and run in the correct order.

The order that migrations are run in is set by the first argument. It is not neccessary that this be unique; migrations with the same version number are expected to be able to be run in any order.

The second argument is the name of the migration. This name is used internally to track if the migration has been run. It is required that this name be unique across all migrations.

Addtionally, it accepts a number of options:

  • :database If you defined several DataMapper::database instances use this to choose which one to run the migration gagainst. Defaults to :default. Migrations are tracked individually per database.

  • :verbose true/false, defaults to true. Determines if the migration should output its status messages when it runs.

Example of a simple migration:

migration( 1, :create_people_table ) do
  up do
    create_table :people do
      column :id,   Integer, :serial => true
      column :name, String, :size => 50
      column :age,  Integer
    end
  end
  down do
    drop_table :people
  end
end

Its recommended that you stick with raw SQL for migrations that manipulate data. If you write a migration using a model, then later change the model, there’s a possibility the migration will no longer work. Using SQL will always work.



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# File 'lib/dm-migrations/migration_runner.rb', line 42

def migration( number, name, opts = {}, &block )
  raise "Migration name conflict: '#{name}'" if migrations.map { |m| m.name }.include?(name.to_s)

  migrations << DataMapper::Migration.new( number, name.to_s, opts, &block )
end

#migrations ⇒ Object 



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# File 'lib/dm-migrations/migration_runner.rb', line 78

def migrations
  @@migrations ||= []
end