Re: Using each rel as both outer and inner for JOIN_ANTI

On Sun, Jul 31, 2022 at 12:07 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:

I took a quick look through this.  The executor changes are indeed
impressively short, but that's largely because you've paid zero
attention to updating obsoleted comments.  For example, in
nodeHashjoin.c there are lots of references to right/full joins
that likely now need to cover right-anti.  I'm not sure that the
empty-rel startup optimizations are correct for this case, either.

Thanks for the review! Yeah, you're right. I neglected to update the
related comments. Will do that in the new patch. For the empty-rel
startup optimizations, since the right-anti join also does null-fill on
inner relation (the HJ_FILL_INNER case), I think we cannot skip building
the hash table even when the outer rel is completely empty.