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From: Dmitry Dolgov <[email protected]>
To: Yasuo Honda <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: Peter Smith <[email protected]>
Cc: vignesh C <[email protected]>
Cc: Michael Paquier <[email protected]>
Cc: Nathan Bossart <[email protected]>
Cc: Gregory Stark (as CFM) <[email protected]>
Cc: David Geier <[email protected]>
Cc: Sergei Kornilov <[email protected]>
Cc: Alvaro Herrera <[email protected]>
Cc: Marcos Pegoraro <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Zhihong Yu <[email protected]>
Cc: David Steele <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Cc: Pavel Trukhanov <[email protected]>
Subject: Re: pg_stat_statements and "IN" conditions
Date: Mon, 25 Mar 2024 17:35:27 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAKmOUTn74jTQAk0u2FUMsGjgrNugLOwkyic2MPkbOJtcQrufeA@mail.gmail.com>
References: <[email protected]>
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> On Sun, Mar 24, 2024 at 11:36:38PM +0900, Yasuo Honda wrote:
> Thanks for the information. I can apply these 4 patches from
> 0eb23285a2 . I tested this branch from Ruby on Rails and it gets some
> unexpected behavior from my point of view.
> Setting pg_stat_statements.query_id_const_merge_threshold = 5 does not
> normalize sql queries whose number of in clauses exceeds 5.
>
> Here are test steps.
> https://gist.github.com/yahonda/825ffccc4dcb58aa60e12ce33d25cd45#expected-behavior
>
> It would be appreciated if I can get my understanding correct.

From what I understand out of the description this ruby script uses
prepared statements, passing values as parameters, right? Unfortunately
the current version of the patch doesn't handle that, it works with
constants only [1]. The original incarnation of this feature was able to
handle that, but the implementation was considered to be not suitable --
thus, to make some progress, it was left outside.

The plan is, if everything goes fine at some point, to do a follow-up
patch to handle Params and the rest.

[1]: https://www.postgresql.org/message-id/20230211104707.grsicemegr7d3mgh%40erthalion.local

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