| From: | Bob Jolliffe <bobjolliffe(at)gmail(dot)com> |
|---|---|
| To: | Michael Christofides <michael(at)pgmustard(dot)com> |
| Cc: | pgsql-performance(at)lists(dot)postgresql(dot)org |
| Subject: | Re: Unaccounted regression from postgresql 11 in later versions |
| Date: | 2023-05-31 10:26:58 |
| Message-ID: | CACd=f9e1T13ChgDUgURit+JaJa2Mo+CeEyz3xKnJibPfOmr21g@mail.gmail.com |
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| Lists: | pgsql-performance |
Wow Michael you are absolutely right. Turning jit off results in a query
execution about twice as fast as pg11. That is a huge relief. I will read
the jit related docs and see if there is anything smarter I should be doing
other than disabling jit entirely, but it works a treat for this query.
Regards
Bob
On Wed, 31 May 2023 at 11:11, Michael Christofides <michael(at)pgmustard(dot)com>
wrote:
> Does anyone have a theory of why pg15 should behave so differently to pg11
>> here? Better still, any suggestions for configuration that might make pg15
>> behave more like pg10. I am really dreading the prospect of stepping our
>> many live implementations back to pg11 :-(.
>>
>
> One major factor here appears to be JIT compilation, which is off by
> default in pg11, but on by default in pg12+.
>
> You can see at the bottom of your slowest query plan that about 233s of
> the 240s are JIT related.
>
> There is good info in the docs about tuning, or turning off, JIT:
> https://www.postgresql.org/docs/current/jit-decision.html
>
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