Re: Query ID Calculation Fix for DISTINCT / ORDER BY and LIMIT / OFFSET

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Sami Imseih <samimseih(at)gmail(dot)com>
Cc: David Rowley <dgrowleyml(at)gmail(dot)com>, Bykov Ivan <i(dot)bykov(at)modernsys(dot)ru>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Query ID Calculation Fix for DISTINCT / ORDER BY and LIMIT / OFFSET
Date: 2025-03-14 00:27:52
Message-ID: Z9N4CF2MM0RR31aD@paquier.xyz
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On Thu, Mar 13, 2025 at 07:17:20PM -0500, Sami Imseih wrote:
>> Then we have the same problem with another Node using this Foo node
>> two times in a row, depending on how it's used by the query parsing
>> and transform:
>
> hmm, it's hard to imagine such a case being real-world and useful for
> query jumbling purposes.

Perhaps, but the code allows that be design, and people like forking
Postgres.

> Also, I think if we introduce something like
> JUMBLE_NULL() or JUMBLE_POSITION(), the author of a custom jumbling
> function should use it. This could be added in code comments somewhere, IMO.

FWIW, another idea I have on top of my mind is the addition of a
counter in JumbleState that we increment each time we enter
_jumbleNode(), then simply call JUMBLE_FIELD_SINGLE() after the
incrementation. And we can rely on this counter to be unique each
time we jumble a node..
--
Michael

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