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.
