Re: BUG #18885: ERROR: corrupt MVNDistinct entry - 2

Hi, Andrei!

On Thu, Apr 10, 2025 at 3:28 PM Andrei Lepikhov <lepihov@gmail.com> wrote:
>
> On 4/9/25 15:46, PG Bug reporting form wrote:
> > The following SQL triggers "ERROR: corrupt MVNDistinct entry", however this
> > seems to be unrelated to a recent bugfix[1] for a similar issue (thus '2' in
> > the $SUBJECT).
> That's my fault.
> We wanted to avoid using of the add_unique_group_var, but forgot it does
> some necessary stuff.
> Here, I attempt to use this routine in the hash join bucket size
> estimation. I transformed it a little, made it more general. Not sure it
> is the best design, but it is debatable.

Thank you for the fix, but it's not enough.

If you would replace a new regression tests query with this, it would
fail with an assertion.

SELECT FROM sb_1 LEFT JOIN sb_2 ON (sb_2.x=sb_1.x) AND (sb_1.x=sb_2.x)
AND (sb_1.y=sb_2.y);

When you use add_unique_group_var() which keeps varinfos unique then
you can no longer expect that varinfos have the same order as
origin_rinfos.

------
Regards,
Alexander Korotkov
Supabase