Re: POC, WIP: OR-clause support for indexes

Hi, Peter!

Thank you very much for the feedback on this patch.

On Fri, Oct 4, 2024 at 8:44 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> On Fri, Oct 4, 2024 at 7:45 AM Alexander Korotkov <aekorotkov(at)gmail(dot)com> wrote:
> > Andrei, thank you for your opinion. Just for the record, I'm still
> > exploring this and will reply later today or tomorrow.
>
> The logic that allows this to work for the case of IN() lists appears
> in transformAExprIn(), which is in parse_expr.c. I wonder if it would
> be possible to do something similar at the point where the patch does
> its conversion to a SAOP. What do you think?

Yes, transformAExprIn() does the work to coerce all the expressions in
the right part to the same type. Similar logic could be implemented
in match_orclause_to_indexcol(). What worries me is whether it's
quite late stage for this kind of work. transformAExprIn() works
during parse stage, when we need to to resolve types, operators etc.
And we do that once. If we replicate the same logic to
match_orclause_to_indexcol(), then we may end up with index scan using
one operator and sequential scan using another operator. Given we
only use implicit casts for types coercion those are suppose to be
strong equivalents. And that's for sure true for builtin types and
operators. But isn't it too much to assume the same for all
extensions?

------
Regards,
Alexander Korotkov
Supabase