On Thu, Jul 22, 2021 at 9:42 AM Tom Lane <t...@sss.pgh.pa.us> wrote: > Right. The point here is that before v13, hash aggregation was not > subject to the work_mem limit, nor any related limit. If you did an > aggregation requiring more than 2GB-plus-slop, it would work just fine > as long as your machine had enough RAM. Now, the performance sucks and > there is no knob you can turn to fix it. That's unacceptable in my book.
Oh! That makes way more sense. I suspect David's theory about hash_agg_set_limits()'s ngroup limit is correct. It certainly seems like a good starting point. -- Peter Geoghegan
