Re: Set query_id for query contained in utility statement

On Mon, Sep 30, 2024 at 5:14 PM jian he <jian.universality@gmail.com> wrote:
> Is it possible to normalize top level utilities explain query, make
> these two have the same queryid?
> explain(verbose) EXECUTE test_prepare_pgss1(1, 2);
> explain(verbose) EXECUTE test_prepare_pgss1(1, 3);
>
> I guess this is a corner case.

This seems to be a known issue. The test_prepare_pgss1's parameters
are A_Const nodes. Those nodes have a custom query jumble which
doesn't record location[1] and thus can't be normalised by pgss.

That could be fixed by replacing the switch on nodeTag by
JUMBLE_LOCATION(location) but this will impact a lot of DDL queries
and the result doesn't look great (for example, "BEGIN TRANSACTION NOT
DEFERRABLE, READ ONLY, READ WRITE, DEFERRABLE" would be normalised as
"BEGIN TRANSACTION $1 DEFERRABLE, $2 ONLY, $3 WRITE, $4")

Looking at the commit for the A_Const's jumble, this is mentioned by Michael[2]:
> (FWIW, I'd like to think that there is an argument to normalize the
> A_Const nodes for a portion of the DDL queries, by ignoring their
> values in the query jumbling and mark a location, which would be
> really useful for some workloads, but that's a separate discussion I
> am keeping for later.)

I haven't found any recent discussion but this should live in a
different thread as this is a separate issue.

[1]:
https://github.com/postgres/postgres/blob/cf4401fe6cf56811343edcad29c96086c2c66481/src/backend/nodes/queryjumblefuncs.c#L323-L355
[2]: https://www.postgresql.org/message-id/Y9+HuYslMAP6yyPb@paquier.xyz