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From: Attila Soki <[email protected]>
To: Andrei Lepikhov <[email protected]>
Cc: [email protected]
Subject: Re: unstable query plan on pg 16,17,18
Date: Tue, 24 Feb 2026 10:16:08 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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On 23 Feb 2026, at 21:25, Andrei Lepikhov <[email protected]> wrote:
> Thanks. But I meant your 'good' plan built by the PG14. I think a new feature invented later has added some problems.
> 
> Current conjecture is the following. As I see, the main problem is with Right Hash Join:
> -> Hash Right Join (cost=210369.25..210370.30 rows=8 width=99)
> Its inner side (Hash table) is rebuilt multiple times (around 1k) due to an external parameter (gauf_1.id) in the subtree. It looks like a disaster, and before I thought we don't build hash tables over parameterised query trees at all.
> 
> So, let me discover a little more, but your PG14 explain could add more details here.

Sorry, I misunderstood that.
here is the pg14.4 explain

https://explain.depesz.com/s/eb32

Regards,
Attila

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