On Fri, 17 Feb 2023 at 13:23, Andres Freund <andres@anarazel.de> wrote:
> But wouldn't an even cheaper way here be to iterate over the children in
> reverse order when match_partition_order_desc? We can do that efficiently
> now. Looks like we don't have a readymade helper for it, but it'd be easy
> enough to add or open code.
That seems fair. I think open coding is a better option. I had a go
at foreach_reverse recently and decided to keep clear of it due to
behavioural differences with foreach_delete_current().
I've attached a patch for this. It seems to have similar performance
to the list_reverse()
$ psql -c "explain (analyze, timing off) select * from lp order by a
desc" postgres | grep "Planning Time"
Planning Time: 522.554 ms <- cold relcache
Planning Time: 467.776 ms
Planning Time: 466.424 ms
David