Wishlist: SQL querylog timings for PDO

[Ben]

Having milliseconds retrieval time in the PDO querylog would shed light on an otherwise dark corner of performance monitoring.

When the MySQL adapter transitioned to PDO, the query log timings were omitted from the log output. The older MySQLi logs included milliseconds elapsed, which was helpful in surfacing retrieval bottlenecks. Attempts to manually profile PDO queries often run up against a profiling_history_size of 100, a limit imposed by MySQL itself. That is to say that getting a complete list of timings over the course of serving a page isn't always easy. Having these added back to the querylog (if possible) would be extremely helpful.