ActiveRecord PostgreSQL automatic timestamps

#
# File:  RAILS_APP_ROOT/lib/extensions/postgres_timestamps.rb
#
# What:  Hack up Rails/AR 3 postgresql adapter to do the following:
#
#          1. Always qualify timestamp types WITH TIME ZONE
#          2. Assign DEFAULT CURRENT_TIMESTAMP to created_at, updated_at
#          3. Assign a special updated_at trigger to tables with that column
#
# Note:  XXX This logic assumes that a pg FUNCTION "ar_trg_updated_at()"
#        exists in the target database !!!
#
#        See also http://stackoverflow.com/questions/5098339/activerecord-pg-support-automatic-timestamps-in-ddl
#
#  How:  This file is require'd in "config/environment.rb" if and only
#        if our connection class' ADAPTER_NAME == 'PostgreSQL'
#

module ActiveRecord
  module ConnectionAdapters

    class PostgreSQLAdapter
      [:datetime, :timestamp].each do |type|
        NATIVE_DATABASE_TYPES[type] = 'TIMESTAMP WITH TIME ZONE'
      end
    end

    class ColumnDefinition
      alias :original_to_sql :to_sql
      def to_sql
        if ['created_at', 'updated_at'].include?(name.to_s)
          "#{base.quote_column_name(name)} #{sql_type} DEFAULT CURRENT_TIMESTAMP"
        else
          original_to_sql
        end
      end
    end

    module SchemaStatements
      alias :original_create_table :create_table
      def create_table(table_name, options = {})
        block = Proc.new rescue Proc.new {|*args| }
        ret = original_create_table(table_name, options, &block)
        if column_exists?(table_name, :updated_at)
          execute <<-eotrigger
            CREATE TRIGGER ar_trg_updated_at
                    BEFORE UPDATE
                        ON #{quote_table_name(table_name)}
              FOR EACH ROW
         EXECUTE PROCEDURE ar_trg_updated_at()
          eotrigger
        end
        ret
      end
    end

  end # -- ConnectionAdapters
end # -- ActiveRecord