On 4 April 2018 at 05:44, Jesper Pedersen <jesper.peder...@redhat.com> wrote: > I have tested this together with Amit's v46 patch.
Thanks for testing this. > The attached case doesn't trigger a generic plan, so basically all time is > spent in GetCachedPlan. Yeah, there's still no resolution to the fact that a generic plan + runtime pruning might be cheaper than a custom plan. The problem is the generic plan appears expensive to the custom vs generic plan comparison due to it containing more Append subnodes and the run-time pruning not being taking into account by that comparison. There's been some discussion about this on this thread somewhere. I think the best solution is probably the one suggested by Robert [1] and that's to alter the Append plan's cost when run-time pruning is enabled to try to account for the run-time pruning. This would be a bit of a blind guess akin to what we do for clause selectivity estimates for Params, but it's probably better than nothing, and likely better than doing nothing. > Also, I'm seeing a regression for check-world in > src/test/regress/results/inherit.out > > *************** > *** 642,648 **** > ---------------------+---+---+----- > mlparted_tab_part1 | 1 | a | > mlparted_tab_part2a | 2 | a | > ! mlparted_tab_part2b | 2 | b | xxx > mlparted_tab_part3 | 3 | a | xxx > (4 rows) > > --- 642,648 ---- > ---------------------+---+---+----- > mlparted_tab_part1 | 1 | a | > mlparted_tab_part2a | 2 | a | > ! mlparted_tab_part2b | 2 | b | > mlparted_tab_part3 | 3 | a | xxx > (4 rows) > > I'll spend some more time tomorrow. Yeah, it's a bug in v46 faster partition pruning. Discussing a fix for that with Amit over on [2]. If you patch v46 with the patch I attached to that thread, it should work. [1] https://www.postgresql.org/message-id/CA%2BTgmoZv8sd9cKyYtHwmd_13%2BBAjkVKo%3DECe7G98tBK5Ejwatw%40mail.gmail.com [2] https://www.postgresql.org/message-id/CAKJS1f_6%2BgXB%3DQ%2BDryeB62yW7N19sY8hH_dBSjPFjm2ifdgoCw%40mail.gmail.com -- David Rowley http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
