Merlin Moncure <mmonc...@gmail.com> writes: > Aside from the functional issues, could your changes result in > performance regressions? (if so, I'd argue not to backpatch unless > there were cases that returned bad data as opposed to spurious > errors).
I can't say that I think planner failures on valid queries is something that's optional to fix. However, I believe that this will typically not change the selected plan in cases where the planner didn't fail before. I did notice one change in an existing regression test, where the planner pushed a qual clause further down in the plan than it did before; but that seems like a better plan anyway. (The reason that happened is that the changes to enlarge the minimum parameterization of some base rels result in choosing to push qualifiers further down, since a qual clause will be evaluated at the lowest plan level that the selected parameterization allows.) It's a little bit harder to gauge the impact on planner speed. The transitive closure calculation could be expensive in a query with many lateral references, but that doesn't seem likely to be common; and anyway we'll buy back some of that cost due to simpler tests later. I'm optimistic that we'll come out ahead in HEAD/9.5 after the removal of LateralJoinInfo setup. It might be roughly a wash in the back branches. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers