#1214 ✓resolved
Daniel Neighman

Migrations broken in rails 3

Reported by Daniel Neighman | March 6th, 2010 @ 05:45 PM | in 1.1

When trying to run a migration in rails 3, the migration breaks because it cannot find the Sql constnat in the adapter. The adapter used is the Benchmark adapter.

The code responsible is in the migration.rb file in the initialize method.

def initialize( position, name, opts = {}, &block )
  @position, @name = position, name
  @options = opts

  @database = DataMapper.repository(@options[:database] || :default)
  @adapter = @database.adapter
  if @adapter.respond_to?(:adapter)
    @adapter = @adapter.adapter

  case @adapter.class.to_s
  when /Sqlite3/  then @adapter.extend(SQL::Sqlite3)
  when /Mysql/    then @adapter.extend(SQL::Mysql)
  when /Postgres/ then @adapter.extend(SQL::Postgresql)
    raise "Unsupported Migration Adapter #{@adapter.class}"

Here, to get around it I've added the:

  if @adapter.respond_to?(:adapter)
    @adapter = @adapter.adapter

portion. This will use the adapter of the benchmark adapter.

Comments and changes to this ticket

  • Daniel Neighman

    Daniel Neighman March 7th, 2010 @ 06:18 AM

    Actually I found this also. I haven't pushed up a patch for this simply because I haven't written tests to make sure it's right. Here's the other piece of my puzzle.

    In the migration runner:

    def migrations
      @@migrations ||= []

    Setting this to a class level variable means that it's stored with the runner class not the instance. This, for me at least, allowed it to run.

  • Martin Gamsjaeger (snusnu)

    Martin Gamsjaeger (snusnu) March 25th, 2010 @ 09:16 AM

    • Milestone set to 1.0.0
    • State changed from “new” to “confirmed”
    • Assigned user set to “Martin Gamsjaeger (snusnu)”
  • Martin Gamsjaeger (snusnu)

    Martin Gamsjaeger (snusnu) March 30th, 2010 @ 09:14 AM

    • State changed from “confirmed” to “accepted”
  • Martin Gamsjaeger (snusnu)

    Martin Gamsjaeger (snusnu) March 30th, 2010 @ 09:56 AM

    • State changed from “accepted” to “resolved”

    This should be fixed in http://github.com/datamapper/dm-rails/commit/a0eb1fd1fbf09c222a7772...

    Marking this resolved for now, please reopen if there are still problems!

  • Xavier Shay

    Xavier Shay September 19th, 2010 @ 05:08 AM

    • State changed from “resolved” to “confirmed”
    • Milestone order changed from “0” to “0”

    I still needed to make the patch suggested by Dan above (change the instance var to a class var) to get these to work. I can't explain why though, I would have expected the instance var to work.

    Have re-opened this issue rather than create a new because I think the history in this ticket is relevant.

  • Xavier Shay

    Xavier Shay September 19th, 2010 @ 07:51 AM

    Here is a rake task I am using to monkey patch the gem to make the rake tasks work from my own code base:

    # Need to be able to monkey-patch MigrationRunner before all migrations
    # are loaded to work around a bug, so replace db:migrate:load with our own
    # version
    # From http://github.com/eugenebolshakov/override_rake_task
    Rake::TaskManager.class_eval do
      def alias_task(old_name, new_name)
        @tasks[new_name] = @tasks.delete(old_name)
    def alias_task(old_name, new_name)
      Rake.application.alias_task(old_name, new_name)
    def override_task(*args, &block)
      name, params, deps = Rake.application.resolve_args(args.dup)
      alias_task name.to_s, "#{name}:original"
      Rake::Task.define_task(*args, &block)
    override_task :'db:migrate:load' => :environment do
      require 'dm-migrations/migration_runner'
      # Original version has an instance var, not a class, and doesn't work
      # for me
      module DataMapper
        module MigrationRunner
          def migrations
            @@migrations ||= []
      # Code from original task
      FileList['db/migrate/*.rb'].each do |migration|
        load migration
  • Piotr Solnica (solnic)

    Piotr Solnica (solnic) October 15th, 2010 @ 05:43 AM

    • Milestone changed from 1.0.0 to 1.1
    • Milestone order changed from “13” to “0”
  • Dan Kubb (dkubb)

    Dan Kubb (dkubb) October 24th, 2010 @ 12:50 PM

    • State changed from “confirmed” to “resolved”

    (from [cd9d62ee08b6615a2d1ab2482b24d72232d867a3]) Store DataMapper::MigrationRunner#migrations in a class variable

    Fixes an issue where migrations don't get run at
    all in dm-rails rake tasks.

    Further explanation can be found in the related
    ticket on LH. This is weird. Maybe it has to do
    something with the way rails loads the rake tasks
    and invokes our stuff. No idea ...

    [#1214 state:resolved] http://github.com/datamapper/dm-migrations/commit/cd9d62ee08b6615a2...

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