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help / color / mirror / Atom feedFrom: Nikolay Samokhvalov <[email protected]>
To: Jerry Brenner <[email protected]>
Cc: [email protected]
Subject: Re: Is there a way to identify a plan generated by GECO?
Date: Thu, 17 Jul 2025 18:43:56 -0700
Message-ID: <CAM527d_cpe_mMrbO4OVLPfZGsF7ukLYA=dPAyeiy-D-smuukAQ@mail.gmail.com> (raw)
In-Reply-To: <CACoKFYRSOZFA0m33BCDHBkget30sY71hMwH9peHvTKxcV6Ha4A@mail.gmail.com>
References: <CACoKFYRSOZFA0m33BCDHBkget30sY71hMwH9peHvTKxcV6Ha4A@mail.gmail.com>
On Thu, Jul 17, 2025 at 18:11 Jerry Brenner <[email protected]> wrote:
> We are on Postgres 15.5 (Aurora) and capturing query plans via
> auto_explain. We are seeing a large number of query plans for 2 queries
> that have 12 tables. Every fast (or "fast enough") plan has a left deep
> tree and every slow plan has a bushy tree. Is there a way to determine if
> a plan was generated by GECO?
>
> We have from_collapse_limit, join_collapse_limit and geqo_threshold all
> set to 12. (There is a COUNT(*) above derived table - could that be
> somehow affecting this?)
>
> I've manually explained plans and haven't seen the problem, but then it
> turns up the next day (with the same parameter values) with multiple
> execution plans.
>
I'm not aware of ability to see if grow was involved, but with Aurora,
should be able can provision a thin (CoW) clone with PITR to a specific
point when you suspect the plan in question was used ("slow") -- and study
the planner behavior in detail, experimenting and adjusting planner
parameters.
Nik
>
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Subject: Re: Is there a way to identify a plan generated by GECO?
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