| From: | Justin Pryzby <pryzby(at)telsasoft(dot)com> |
|---|---|
| To: | johannes graën <johannes(at)selfnet(dot)de> |
| Cc: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: performance drop after upgrade (9.6 > 10) |
| Date: | 2017-10-26 19:45:15 |
| Message-ID: | 20171026194515.GV21735@telsasoft.com |
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| Thread: | |
| Lists: | pgsql-hackers pgsql-performance |
On Tue, Oct 24, 2017 at 04:15:59PM +0200, johannes graën wrote:
> Hi Pavel, *,
>
> you were right with ANALYZing the DB first. However, even after doing
> so, I frequently see Seq Scans where an index was used before. This
> usually cooccurs with parallelization and looked different before
> upgrading to 10. I can provide an example for 10 [1], but I cannot
> generate a query plan for 9.6 anymore.
>
> Any ideas what makes the new version more seqscanny?
Is it because max_parallel_workers_per_gather now defaults to 2 ?
BTW, I would tentatively expect a change in default to be documented in the
release notes but can't see that it's.
77cd477c4ba885cfa1ba67beaa82e06f2e182b85
Justin
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