Horton

Re: queryId constant squashing does not support prepared statements

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Sami Imseih <samimseih@gmail.com>
Cc: Dmitry Dolgov <9erthalion6@gmail.com>, Álvaro Herrera <alvherre@kurilemu.de>, Junwang Zhao <zhjwpku@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2025-05-27T00:58:34Z
Lists: pgsql-hackers

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  1. Fix typo in comment

  2. Make query jumbling also squash PARAM_EXTERN params

  3. Fix squashing algorithm for query texts

  4. pg_stat_statements: Fix parameter number gaps in normalized queries

On Sat, May 24, 2025 at 09:35:24AM -0500, Sami Imseih wrote:
> 2. If we have 1 or more squashed lists, then we can't guarantee
> the $n parameter as was supplied by the user and we simply rename
> the $n starting from 1.
> 
> therefore, a user supplied query like this:
> ```
> select where $5 in ($1, $2, $3) and $6 = $4 and 1 = 2
> ```
> 
> will be normalized to:
> ```
> select where $1 in ($2 /*...*/) and $3 = $4 and $5 = $6
> ```
> 
> To accomplish this, we will need to track the locations of
> external parameters to support the 2nd case, because we need
> to re-write the original location of the parameter with
> the new value. I played around with this this morning and
> it works as I described above. Any concerns with the
> behavior described above?

That would be OK by me.  Not having gaps in the parameter numbers of
the normalized query just feels just like the natural thing to have in
the data reported by PGSS.
--
Michael