Jim Nasby <jim.na...@bluetreble.com> writes: > On 2/14/17 1:18 PM, Tom Lane wrote: >> One point that could use further review is whether the de-duplication >> algorithm is actually correct. I'm only about 95% convinced by the >> argument I wrote in planunionor.c's header comment.
> I'll put some thought into it and see if I can find any holes. Are you > only worried about the removal of "useless" rels or is there more? Well, the key point is whether it's really OK to de-dup on the basis of only the CTIDs that are not eliminated in any UNION arm. I was feeling fairly good about that until I thought of the full-join-to- left-join-to-no-join conversion issue mentioned in the comment. Now I'm wondering if there are other holes; or maybe I'm wrong about that one and it's not necessary to be afraid of full joins. regards, tom lane -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers