On 2016-04-13 13:52:15 -0500, Kevin Grittner wrote: > On Wed, Apr 13, 2016 at 12:25 PM, Robert Haas <robertmh...@gmail.com> wrote: > > > [test results with old_snapshot_threshold = 0 and 10] > > From the docs: > > | A value of -1 disables this feature, and is the default.
Hm, ok, let me run that as well then. The reason for the massive performance difference presumably is that MaintainOldSnapshotTimeMapping() is cut short due to /* No further tracking needed for 0 (used for testing). */ if (old_snapshot_threshold == 0) return; which means that OldSnapshotTimeMap isn't acquired exclusively. > > Yuck. Aside from the fact that performance tanks when the feature is > > turned on, it seems that there is a significant effect even with it > > turned off. > > No evidence of that has been provided. -1 is off; 0 is for testing > very fast expiration. I'll run with -1 once the current (longer) run has finished. Greetings, Andres Freund -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers