Re: Functional dependencies and GROUP BY

Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> Next version. Changed dependencies to pg_constraint, removed handling
> of unique constraints for now, and made some enhancements so that views
> track dependencies on constraints even in subqueries. Should be close
> to final now. :-)

I've committed this with some revisions, notably:

The view.c changes were fundamentally wrong. The right place to
extract dependencies from a parsetree is in dependency.c, specifically
find_expr_references_walker. The way you were doing it meant that
dependencies on constraints would only be noticed for views, not for
other cases such as stored plans.

I rewrote the catalog search to look only at pg_constraint, not using
pg_index at all. I think this will be easier to extend to the case of
looking for UNIQUE + NOT NULL, whenever we get around to doing that.
I also moved the search into catalog/pg_constraint.c, because it didn't
seem to belong in parse_agg (as hinted by the large number of #include
additions you had to make to put it there).

I put in a bit of caching logic to prevent repeating the search for
multiple Vars of the same relation. Tests or no tests, I can't believe
that's going to be cheap enough that we want to repeat it over and
over...

regards, tom lane