On 1/25/17 12:43, Simon Riggs wrote: > On 25 January 2017 at 17:34, Julian Markwort > <julian.markw...@uni-muenster.de> wrote: > >> Analogous to this, a bad_plan is saved, when the time has been exceeded by a >> factor greater than 1.1 . > ...and the plan differs? > > Probably best to use some stat math to calculate deviation, rather than fixed > %.
Yeah, it seems to me too that this needs a bit more deeper analysis. I don't see offhand why a 10% deviation in execution time would be a reasonable threshold for "good" or "bad". A deviation approach like you allude to would be better. The other problem is that this measures execution time, which can vary for reasons other than plan. I would have expected that the cost numbers are tracked somehow. There is also the issue of generic vs specific plans, which this approach might be papering over. Needs more thought. -- Peter Eisentraut http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
