instance method indexes

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 173
        def indexes(table_name, name = nil)
          table = Utils.extract_schema_qualified_name(table_name.to_s)

          result = query(<<-SQL, 'SCHEMA')
            SELECT distinct i.relname, d.indisunique, d.indkey, pg_get_indexdef(d.indexrelid), t.oid,
                            pg_catalog.obj_description(i.oid, 'pg_class') AS comment,
            (SELECT COUNT(*) FROM pg_opclass o
               JOIN (SELECT unnest(string_to_array(d.indclass::text, ' '))::int oid) c
                 ON o.oid = c.oid WHERE o.opcdefault = 'f')
            FROM pg_class t
            INNER JOIN pg_index d ON t.oid = d.indrelid
            INNER JOIN pg_class i ON d.indexrelid = i.oid
            LEFT JOIN pg_namespace n ON n.oid = i.relnamespace
            WHERE i.relkind = 'i'
              AND d.indisprimary = 'f'
              AND t.relname = '#{table.identifier}'
              AND n.nspname = #{table.schema ? "'#{table.schema}'" : 'ANY (current_schemas(false))'}
            ORDER BY i.relname
          SQL

          result.map do |row|
            index_name = row[0]
            unique = row[1]
            indkey = row[2].split(" ").map(&:to_i)
            inddef = row[3]
            oid = row[4]
            comment = row[5]
            opclass = row[6]

            using, expressions, where = inddef.scan(/ USING (\w+?) \((.+?)\)(?: WHERE (.+))?\z/).flatten

            if indkey.include?(0) || opclass > 0
              columns = expressions
            else
              columns = Hash[query(<<-SQL.strip_heredoc, "SCHEMA")].values_at(*indkey).compact
                SELECT a.attnum, a.attname
                FROM pg_attribute a
                WHERE a.attrelid = #{oid}
                AND a.attnum IN (#{indkey.join(",")})
              SQL

              # add info on sort order for columns (only desc order is explicitly specified, asc is the default)
              orders = Hash[
                expressions.scan(/(\w+) DESC/).flatten.map { |order_column| [order_column, :desc] }
              ]
            end

            IndexDefinition.new(table_name, index_name, unique, columns, [], orders, where, nil, using.to_sym, comment.presence)
          end.compact
        end