Re: [PERFORM] performance drop after upgrade (9.6 > 10) - Mailing list pgsql-performance

From Justin Pryzby
Subject Re: [PERFORM] performance drop after upgrade (9.6 > 10)
Date
Msg-id 20171026194515.GV21735@telsasoft.com
Whole thread Raw
In response to Re: [PERFORM] performance drop after upgrade (9.6 > 10)  (johannes graën <johannes@selfnet.de>)
Responses Re: [PERFORM] performance drop after upgrade (9.6 > 10)
List 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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