pt-query-digest 值得拥有

      --since
           type: string

           Parse only queries newer than this value (parse queries since this date).

           This option allows you to ignore queries older than a certain value and parse only those queries which are more recent than the value.  The value can be several
           types:

             * Simple time value N with optional suffix: N[shmd], where
               s=seconds, h=hours, m=minutes, d=days (default s if no suffix
               given); this is like saying "since N[shmd] ago"
             * Full date with optional hours:minutes:seconds:
               YYYY-MM-DD [HH:MM:SS]
             * Short, MySQL-style date:
               YYMMDD [HH:MM:SS]
             * Any time expression evaluated by MySQL:
               CURRENT_DATE - INTERVAL 7 DAY

           If you give a MySQL time expression, and you have not also specified a DSN for "--explain", "--processlist", or "--review", then you must specify a DSN on the
           command line so that pt-query-digest can connect to MySQL to evaluate the expression.

           The MySQL time expression is wrapped inside a query like "SELECT UNIX_TIMESTAMP(<expression>)", so be sure that the expression is valid inside this query.  For
           example, do not use UNIX_TIMESTAMP() because UNIX_TIMESTAMP(UNIX_TIMESTAMP()) returns 0.

           Events are assumed to be in chronological: older events at the beginning of the log and newer events at the end of the log.  "--since" is strict: it ignores all
           queries until one is found that is new enough.  Therefore, if the query events are not consistently timestamped, some may be ignored which are actually new
           enough.

           See also "--until".