On Mon, Jul 7, 2014 at 4:15 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > David Rowley <dgrow...@gmail.com> writes: > > On 6 July 2014 03:20, Tom Lane <t...@sss.pgh.pa.us> wrote: > >> Just to note that I've started looking at this, and I've detected a > rather > >> significant omission: there's no check that the join operator has > anything > >> to do with the subquery's grouping operator. > > > hmm, good point. If I understand this correctly we can just ensure that > the > > same operator is used for both the grouping and the join condition. > > Well, that's sort of the zero-order solution, but it doesn't work if the > join operators are cross-type. > > I poked around to see if we didn't have some code already for that, and > soon found that not only do we have such code (equality_ops_are_compatible) > but actually almost this entire patch duplicates logic that already exists > in optimizer/util/pathnode.c, to wit create_unique_path's subroutines > query_is_distinct_for et al. So I'm thinking what this needs to turn into > is an exercise in refactoring to allow that logic to be used for both > purposes. > > Well, it seems that might just reduce the patch size a little! I currently have this half hacked up to use query_is_distinct_for, but I see there's no code that allows Const's to exist in the join condition. I had allowed for this in groupinglist_is_unique_on_restrictinfo() and I tested it worked in a regression test (which now fails). I think to fix this, all it would take would be to modify query_is_distinct_for to take a list of Node's rather than a list of column numbers then just add some logic that skips if it's a Const and checks it as it does now if it's a Var Would you see a change of this kind a valid refactor for this patch?
I notice that create_unique_path is not paying attention to the question > of whether the subselect's tlist contains SRFs or volatile functions. > It's possible that that's a pre-existing bug. > > *shrug*, perhaps the logic for that is best moved into query_is_distinct_for then? It might save a bug in the future too that way. Regards David Rowley
