Re: pg18 bug? SELECT query doesn't work

Eric Ridge <eebbrr(at)gmail(dot)com> writes:
> Here's an even more reduced test case. No tables or data:

> # SELECT * FROM (SELECT upper(unnest(ARRAY['cat', 'dog'])) as animal FROM generate_series(1, 10) GROUP BY 1) x WHERE animal ilike 'c%';

> pg15 returns:

> animal
> --------
> CAT
> (1 row)

> and pg18 says:

> # SELECT * FROM (SELECT upper(unnest(ARRAY['cat', 'dog'])) as animal FROM generate_series(1, 10) GROUP BY 1) x WHERE animal ilike 'c%';
> ERROR: set-valued function called in context that cannot accept a set
> LINE 1: SELECT * FROM (SELECT upper(unnest(ARRAY['cat', 'dog'])) as ...
> ^

I agree that this is a bug. "git bisect" says it broke at

247dea89f7616fdf06b7272b74abafc29e8e5860 is the first bad commit
commit 247dea89f7616fdf06b7272b74abafc29e8e5860 (HEAD)
Author: Richard Guo <rguo(at)postgresql(dot)org>
Date: Tue Sep 10 12:35:34 2024 +0900

Introduce an RTE for the grouping step

I've not probed further than that, but my guess is that now we check
for set-returning tlist items while the tlist still has grouping Vars,
thus missing the fact that there's a SRF represented by one of those
Vars. This prompts us to flatten a subquery we shouldn't have
flattened (because that ends by introducing a SRF into the outer
WHERE).

regards, tom lane