instance method indexes

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 644
      def indexes(table_name, name = nil)
         schemas = schema_search_path.split(/,/).map { |p| quote(p) }.join(',')
         result = query(<<-SQL, name)
           SELECT distinct i.relname, d.indisunique, d.indkey, t.oid
             FROM pg_class t, pg_class i, pg_index d
           WHERE i.relkind = 'i'
             AND d.indexrelid = i.oid
             AND d.indisprimary = 'f'
             AND t.oid = d.indrelid
             AND t.relname = '#{table_name}'
             AND i.relnamespace IN (SELECT oid FROM pg_namespace WHERE nspname IN (#{schemas}) )
          ORDER BY i.relname
        SQL


        result.map do |row|
          index_name = row[0]
          unique = row[1] == 't'
          indkey = row[2].split(" ")
          oid = row[3]

          columns = Hash[query(<<-SQL, "Columns for index #{row[0]} on #{table_name}")]
          SELECT a.attnum, a.attname
          FROM pg_attribute a
          WHERE a.attrelid = #{oid}
          AND a.attnum IN (#{indkey.join(",")})
          SQL

          column_names = columns.values_at(*indkey).compact
          column_names.empty? ? nil : IndexDefinition.new(table_name, index_name, unique, column_names)
        end.compact
      end