How to read constraints direct from postgresql databases

gistfile1.rb

# == Schema Information
#
# Table name: information_schema.table_constraints
#
#  constraint_catalog :
#  constraint_schema  :
#  constraint_name    :
#  table_catalog      :
#  table_schema       :
#  table_name         :
#  constraint_type    :string
#  is_deferrable      :string
#  initially_deferred :string
#

class TableConstraint < ActiveRecord::Base
  set_table_name 'information_schema.table_constraints'

  scope :foreign_keys, where('constraint_type = ?', 'FOREIGN KEY')
  scope :primary_keys, where('constraint_type = ?', 'PRIMARY KEY')

  def self.exists?(conditions)
    self.count(:conditions => conditions) > 0
  end
end