Horton

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

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Bykov Ivan <i.bykov@modernsys.ru>
Cc: David Rowley <dgrowleyml@gmail.com>, Sami Imseih <samimseih@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2025-03-17T09:03:37Z
Lists: pgsql-hackers 
On Mon, Mar 17, 2025 at 07:33:42AM +0000, Bykov Ivan wrote:
> See:
> https://www.postgresql.org/message-id/flat/5ac172e0b77a4baba50671cd1a15285f%40localhost.localdomain#6c43f354f5f42d2a27e6824faa660a86
> 
> Is it really worth spending extra execution time to increase entropy
> when we have non-NULL nodes?

The computed time is already quite cheap, so I'm not much worried
about that, FWIW.

> We could also add entropy if we see a change in the node->type value for
> non-NULL variants.

I am not sure to get this one.  The issue shows up if we have the same
Node computed successively as reported on this thread.  It would still
be a problem for different node types, though less likely, when two
nodes use with similar fields.
--
Michael

Commits

  1. Optimize Query jumble