| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> |
| Cc: | Justin Pryzby <pryzby(at)telsasoft(dot)com>, Sanyo Moura <sanyo(dot)moura(at)tatic(dot)net>, jeff(dot)janes(at)gmail(dot)com, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>, pgsql-performance(at)lists(dot)postgresql(dot)org, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Query with high planning time at version 11.1 compared versions 10.5 and 11.0 |
| Date: | 2018-12-06 07:57:26 |
| Message-ID: | 20181206075726.pig32e6thltb56hr@alvherre.pgsql |
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| Lists: | pgsql-hackers pgsql-performance |
On 2018-Dec-06, Amit Langote wrote:
> The partitionwise join related
> changes in PG 11 moved the add_child_rel_equivalences call in
> set_append_rel_size such that child EC members would be added even before
> checking if the child rel is dummy, but for a reason named in the comment
> above the call:
>
> ... Even if this child is
> * deemed dummy, it may fall on nullable side in a child-join, which
> * in turn may participate in a MergeAppend, where we will need the
> * EquivalenceClass data structures.
>
> However, I think we can skip adding the dummy child EC members here and
> instead make it a responsibility of partitionwise join code in joinrels.c
> to add the needed EC members. Attached a patch to show what I mean, which
> passes the tests and gives this planning time:
Robert, Ashutosh, any comments on this? I'm unfamiliar with the
partitionwise join code.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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