On Fri, Apr 3, 2020 at 12:08 PM David Rowley <dgrowle...@gmail.com> wrote:
> On Fri, 3 Apr 2020 at 16:40, Tom Lane <t...@sss.pgh.pa.us> wrote: > > (It occurs to me BTW that we've been overly conservative about using > > NOT NULL constraints in planning, because of failing to consider that. > > Addition or drop of NOT NULL has to cause a change in > > pg_attribute.attnotnull, which will definitely cause a relcache inval > > on its table, cf rules in CacheInvalidateHeapTuple(). So we *don't* > > need to have a pg_constraint entry corresponding to the NOT NULL, as > > we've mistakenly supposed in some past discussions.) > > Agreed for remove_useless_groupby_columns(), but we'd need it if we > wanted to detect functional dependencies in > check_functional_grouping() using unique indexes. > Thanks for the explanation. I will add the removal in the next version of this patch. Best Regards Andy Fan
