| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, Mladen Gogala <gogala(dot)mladen(at)gmail(dot)com>, pgsql-performance(at)lists(dot)postgresql(dot)org |
| Subject: | Re: Catching up with performance & PostgreSQL 15 |
| Date: | 2022-11-29 14:31:36 |
| Message-ID: | 871130.1669732296@sss.pgh.pa.us |
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| Lists: | pgsql-performance |
Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> writes:
> IMO it was a mistake to turn JIT on in the default config, so that's one
> thing you'll likely want to change.
I wouldn't necessarily go quite that far, but I do think that the
default cost thresholds for invoking it are enormously too low,
or else there are serious bugs in the cost-estimation algorithms
for deciding when to use it. A nearby example[1] of a sub-1-sec
partitioned query that took 30sec after JIT was enabled makes me
wonder if we're accounting correctly for per-partition JIT costs.
regards, tom lane
[1] https://www.postgresql.org/message-id/B6025887-D73F-4B5B-9925-4DA4B675F7E5%40elevated-dev.com
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