Show 10 queries that have longest execution time in aggregate. Requires
        the pg_stat_statments Postgres module to be installed.

        Record(
            qry='UPDATE pgbench_tellers SET tbalance = tbalance + ?;',
            exec_time=datetime.timedelta(0, 19944, 993099),
            prop_exec_time='67.1%',
            ncalls='845589',
            sync_io_time=datetime.timedelta(0)
        )

        :param truncate: trim the Record.qry output if greater than 40 chars
        :returns: list of Records

def outliers(self, truncate=False):
        """
        Show 10 queries that have longest execution time in aggregate. Requires
        the pg_stat_statments Postgres module to be installed.

        Record(
            qry='UPDATE pgbench_tellers SET tbalance = tbalance + ?;',
            exec_time=datetime.timedelta(0, 19944, 993099),
            prop_exec_time='67.1%',
            ncalls='845589',
            sync_io_time=datetime.timedelta(0)
        )

        :param truncate: trim the Record.qry output if greater than 40 chars
        :returns: list of Records
        """

        if self.pg_stat_statement():
            if truncate:
                query = """
                    CASE WHEN length(query) < 40
                        THEN query
                        ELSE substr(query, 0, 38) || '..'
                    END
                """
            else:
                query = 'query'

            return self.execute(sql.OUTLIERS.format(query=query))
        else:
            return [self.get_missing_pg_stat_statement_error()]