Re: queryId constant squashing does not support prepared statements

On 2025-Jun-25, Michael Paquier wrote:

> On Tue, Jun 24, 2025 at 07:45:15PM +0200, Alvaro Herrera wrote:
> > + /*
> > + * If we have an external param at this location, but no lists are
> > + * being squashed across the query, then we skip here; this will make
> > + * us print print the characters found in the original query that
> > + * represent the parameter in the next iteration (or after the loop is
> > + * done), which is a bit odd but seems to work okay in most cases.
> > + */
> > + if (jstate->clocations[i].extern_param && !jstate->has_squashed_lists)
> > + continue;
>
> + * us print print the characters found in the original query that
>
> The final commit includes this comment, with a s/print print/print/
> required.

Ugh. Fixed, thanks for noticing that.

> > Lastly, I decided not to do a catversion bump. As far as I can tell,
> > changes in the jumbling functions do not need them. I tried an
> > 'installcheck' run with a datadir initdb'd with the original code, and
> > it works fine.
>
> This reminds me of 4c7cd07aa62a and this thread:
> https://www.postgresql.org/message-id/1364409.1727673407@sss.pgh.pa.us
>
> Doesn't the change in the Param structure actually require one because
> it can change the representation of some SQL functions? I am not
> completely sure.

Hmm, but the Param structure didn't actually change; only its jumbling
function did (and others that rely on LocationLen). So I think what
could happen here if there's no catversion is that somebody has a
pg_stat_statements populated with query Ids for some queries that have a
different queryIds when computed with the new code. So they're going to
have duplicates in pg_stat_statements. I think this is a pretty minor
problem, so I'm not inclined to do a catversion bump for it.

Anyway we have one due to 0cd69b3d7ef3, so it's moot now. (But it's a
good discussion to have, for the future.)

--
Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/
"Niemand ist mehr Sklave, als der sich für frei hält, ohne es zu sein."
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(Johann Wolfgang von Goethe)