Sho Fukamachi Online

Want to use PostgreSQL’s native UUID datatype but AR won’t let you use it with migrations?

/Library/Ruby/Gems/1.8/gems/activerecord-2.0.2/lib/active_record/connection_adapters/postgresql_adapter.rb:

# insert into
def simplified_type
  # UUID type
  when /^uuid$/
  :uuid
# insert into
def native_database_types
  :uuid      => { :name => "uuid" },

Well, that’ll get your data OUT of the database, but AR will throw a fit when you try to load it back in unless you also add uuid into the range of column types TableDefinition will accept:

in /Library/Ruby/Gems/1.8/gems/activerecord-2.0.2
/lib/active_record/connection_adapters/abstract/schema_definition.rb:

# insert into
def column(name, type, options = {})
 
%w( string text integer float decimal datetime timestamp time date binary boolean uuid ).each do |column_type|

Now you can do this:

    t.uuid     "uuid",   :null => false

About the nastiest possible hack you can do but works in/out. Here’s a patch if you don’t want to do it yourself, but no guarantees.

UPDATE:

And don’t forget to write your migrations like this to stop AR from inserting its “helpful” id columns with autoincrementing serials which your DB doesn’t need and can’t use:

  def self.up
    create_table :transactions, :id => false do |t|
      t.uuid     "id",  :null => false
      t.timestamps
    end
  end

UPDATE 2:

I now do not recommend doing this. It’s more trouble than it’s worth. There is very little you gain in forcing native UUID type in Postgres, and the complexity, hacks, loss of cross-platform compatibility and general annoyance you face are just not worth it.

Just use a string class for any UUIDs. Of course, the final hint on this page – the no-id switch for migrations – is still useful and you should use that.

Tags: activerecord, datatypes, postgresql, schemadumper

This entry was posted on Monday, February 11th, 2008 at 11:50 pm and is filed under development, rails. You can follow any responses to this entry through the feed. You can leave a response, or trackback from your own site.