Re: WIP: Aggregation push-down

>
> > 1) v14-0001-Introduce-RelInfoList-structure.patch
> > -------------------------------------------------
> >
> > - I'm not entirely sure why we need this change. We had the list+hash
> > before, so I assume we do this because we need the output functions?
>
> I believe that this is what Tom proposed in [1], see "Maybe an appropriate
> preliminary patch is to refactor the support code ..." near the end of that
> message. The point is that now we need two lists: one for "plain" relations
> and one for grouped ones.
>
>
I guess what Toms suggested[1] is to store the the grouped ones into
root->upper_rels rather than a separated member, see fetch_upper_rel
or UpperRelationKind. If we do need the list+hash method for long list
lookup,
we can merge it into upper_rels. If we want this benefits at other place
rather
than root->upper_rels, we can store a generic type in RelInfoList, looks
currently
it is bounded to RelAggInfo besides RelOptInfo. But overall, personally I
think we can
ignore such optimization at the first stage to save the attention of the
core reviewers
since they are too precious :) Just FYI

[1] https://www.postgresql.org/message-id/9726.1542577439@sss.pgh.pa.us

Best Regards
Andy Fan