| From: | Adam Brusselback <adambrusselback(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Query much slower after upgrade to 9.6.1 |
| Date: | 2016-11-07 19:26:49 |
| Message-ID: | CAMjNa7ewQTf=MOo0emRPiaYm0J-8beqT6OrNjeaQyE7WP+YWNQ@mail.gmail.com |
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| Lists: | pgsql-performance |
>
> If the problem is "new server won't use hashagg", I'd wonder whether
> the work_mem setting is the same, or whether maybe you need to bump
> it up some (the planner's estimate of how big the hashtable would be
> might have changed a bit).
>
I actually was speaking with Stephen Frost in the slack channel, and tested
both of those theories.
The work_mem was the same between the two servers (12MB), but he suggested
I play around with it. I tried 4MB, 20MB, and 128MB. There was no
difference from 12MB with any of them.
I have my default_statistics_target set to 300, and ran a VACUUM ANALYZE
right after the upgrade to 9.6.1. He suggested I lower it, so I put it
back down to 100, ran a VACUUM ANALYZE, and observed no change in query. I
also tried going the other way and set it to 1000, VACUUM ANALYZE, and
again, no difference to query.
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