Re: 9.6 query slower than 9.5.3 - Mailing list pgsql-performance

From Tom Lane
Subject Re: 9.6 query slower than 9.5.3
Date
Msg-id 8983.1466135852@sss.pgh.pa.us
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In response to Re: 9.6 query slower than 9.5.3  (Adam Brusselback <adambrusselback@gmail.com>)
Responses Re: 9.6 query slower than 9.5.3
List pgsql-performance
Adam Brusselback <adambrusselback@gmail.com> writes:
> Alright with that off I get:
> ...
> Way better.

OK, that confirms the suspicion that beta1's FK-join-estimation logic
is the culprit here.  We had already decided that that logic is broken,
and there's a rewrite in progress:
https://www.postgresql.org/message-id/15245.1466031608%40sss.pgh.pa.us

I wonder though whether the rewrite will fix your example.  Could you
either make some test data available, or try HEAD + aforesaid patch
to see if it behaves sanely on your data?

            regards, tom lane


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