Re: BUG #18277: Unexpected error: "WindowFunc not found in subplan target lists" triggered by JOIN and Window Func

On Tue, Jan 9, 2024 at 7:00 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:

> PG Bug reporting form <noreply@postgresql.org> writes:
> > My fuzzer finds a bug in Postgres 17devel, which triggers an unexpected
> > error "ERROR: WindowFunc not found in subplan target lists".
>
> Thanks for the report!  Bisecting says this broke at
>
> 2489d76c4906f4461a364ca8ad7e0751ead8aa0d is the first bad commit
> commit 2489d76c4906f4461a364ca8ad7e0751ead8aa0d
> Author: Tom Lane <tgl@sss.pgh.pa.us>
> Date:   Mon Jan 30 13:16:20 2023 -0500
>
>     Make Vars be outer-join-aware.


I think this is caused by that query_tree_mutator fails to mutate
runCondition for WindowClause.  So when we've reduced the ref_0/ref_1
left join to inner join, we fail to remove references to this join as
nulling rels in the run condition '1 >= ntile(ref_1.vkey) OVER (?)'.

So maybe we can fix this issue by:

@@ -3641,6 +3646,7 @@ query_tree_mutator_impl(Query *query,
            FLATCOPY(newnode, wc, WindowClause);
            MUTATE(newnode->startOffset, wc->startOffset, Node *);
            MUTATE(newnode->endOffset, wc->endOffset, Node *);
+           MUTATE(newnode->runCondition, wc->runCondition, List *);

I think we should also consider WindowClause->runCondition in
query_tree_walker, expression_tree_mutator and expression_tree_walker.
Hence, proposed the attached patch.

Thanks
Richard