Robert Haas <robertmh...@gmail.com> writes: > ... it's > always struck me as a little unfortunate that we basically test > whether a var is equal by testing whether the varno and varlevelsup > are equal. That only works if you assume that you can never end up > comparing two vars from thoroughly unrelated parts of the tree, such > that the subquery one level up from one might be different from the > subquery one level up from the other.
Yeah, that's always bothered me a little as well. I've yet to see a case where it causes a problem in practice. But I think that if, say, we were to try to do any sort of cross-query-level optimization, then the ambiguity could rise up to bite us. That might be a situation where a flat rangetable would be worth the trouble. > I'm just uncertain whether what Amit has implemented is the > least-annoying way to go about it... any thoughts on that, > specifically as it pertains to this patch? I haven't looked at this patch at all. I'll try to make some time for it, but probably not today. regards, tom lane