On Wed, Sep 11, 2024 at 11:43 AM Richard Guo <guofengli...@gmail.com> wrote: > In some cases, we may want to transfer a HAVING clause into WHERE in > hopes of eliminating tuples before aggregation instead of after. > > Previously, we couldn't do this if there were any nonempty grouping > sets, because we didn't have a way to tell if the HAVING clause > referenced any columns that were nullable by the grouping sets, and > moving such a clause into WHERE could potentially change the results. > > Now, with expressions marked nullable by grouping sets with the RT > index of the RTE_GROUP RTE, it is much easier to identify those > clauses that reference any nullable-by-grouping-sets columns: we just > need to check if the RT index of the RTE_GROUP RTE is present in the > clause. For other HAVING clauses, they can be safely pushed down. > > I'm not sure how common it is in practice to have a HAVING clause > where all referenced columns are present in all the grouping sets. > But it seems to me that this optimization doesn't cost too much. Not > implementing it seems like leaving money on the table.
I've gone ahead and pushed this. Thanks Richard
