ActiveRecord Beta 4 does not understand most postgres data types

I have a postgres database with a table that has a column of type search_vector (and other postgres-specific data geometry data types). Up to Rails 2.3.8 everything was fine, but when I tried upgrading to Rails beta 4 with Arel 0.4.0 I can no longer perform basic queries. The error I get is:

Column type `` is not currently handled

The offending code is in lib/arel/engines/sql/attributes.rb:

module Arel
  module Sql
    module Attributes
      def self.for(column)
        case column.type
        when :string    then String
        when :text      then String
        when :integer   then Integer
        when :float     then Float
        when :decimal   then Decimal
        when :date      then Time
        when :datetime  then Time
        when :timestamp then Time
        when :time      then Time
        when :binary    then String
        when :boolean   then Boolean
        else
          raise NotImplementedError, "Column type `#{column.type}` is not currently handled"
        end
      end
      # ...
    end
  end
end

The column in question looked like this:

#<ActiveRecord::ConnectionAdapters::PostgreSQLColumn:0x34d4a24 @precision=nil, @null=true, @primary=nil, @sql_type="tsvector", @limit=nil, @default=nil, @type=nil, @name="search_vector", @scale=nil>

So there are a few parts to fixing this bug:

• fixing the useless error message when it can't understand a column type
• making AR use the postgres adapter's column types that were used in previous versions of rails

I'd like to fix this, but before I dig in I'd like some feedback on how. A few things that come to mind are:

• Find all places where arel_attributes_values is used and instead call the adapter-specific methods
• Create a new Arel Engine for postgres that inherits from the SQL engine, and overrides methods as necessary (then set the correct engine for each connection)
• Move all the adapter-specific code to Arel
• Making it possible for developers to register their own datatype mapppings without mucking with private apis

If you have an idea what the long-term vision is for making AR work across adapters please let me know. Otherwise, I'll fix this the quickest way I can find and submit a patch. Until then, anybody taking advantage of postgres's other data types is hosed.