Add Postgresql RETURNING <column> to ActiveRecord when updating more than a single row

update_all_returning.rb

# USAGE:
#
# class SomeModel < ActiveRecord::Base
#   include ActiveRecord::PostgresqlExtensions
# end
#
# SomeModel.update_all_returning("count = count + 1", nil, ["id", "count"])
#
module ActiveRecord
  module PostgresqlExtensions  
    def self.included base
      base.send :extend, ClassMethods
    end
  
    module ClassMethods
      def update_all_returning(updates, conditions = nil, returning_columns = [])
        raise ActiveRecord::ActiveRecordError, "Adapter is not PostgreSQL" unless connection.adapter_name == 'PostgreSQL'
        raise TypeError, "can't convert #{returning_columns.class} into Array" unless returning_columns.class == Array
        returning_columns = returning_columns.map{ |x| connection.quote_string(x) }

        sql = "UPDATE #{quoted_table_name} SET #{sanitize_sql_for_assignment(updates)} "
        sql << "WHERE " << sanitize_sql_for_conditions(conditions)
        sql << " RETURNING #{returning_columns.join(', ')}" if returning_columns.length > 0

        res = connection.execute(sql, "#{name} Update")
        connection.result_as_array(res)
      end      
    end
  end
end