| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Bruce Momjian <bruce(at)momjian(dot)us> |
| Cc: | pgsql-hackers(at)lists(dot)postgresql(dot)org, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Caching query plan costs |
| Date: | 2018-09-03 21:53:59 |
| Message-ID: | 20180903215359.5rssotampm35xz5v@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
On 2018-09-03 14:56:28 -0400, Bruce Momjian wrote:
> On Mon, Sep 3, 2018 at 11:42:31AM -0700, Andres Freund wrote:
> > > and JIT, so it doesn't have to be 100% accurate.
> >
> > JIT decision is done after main planning, so we know the cost.
>
> Well, as I remember, we are considering disabling JIT in PG 11 because
> of the use of fixed costs to trigger it. Could executor information
> help decide to use JIT?
I don't think so. The issues with JIT planning are more that it's
costing is simplistic (for good-ish reason, to avoid increasing the
number of plans), and that there's no caching (lots of infrastructure
work needed).
Greetings,
Andres Freund
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