Re: Optimizer Doesn't Push Down Where Expressions on Rollups

In your case, the WHERE clauses would get pushed down into the subquery
for both queries, with/without the ROLLUP. But since the subquery uses
grouping/grouping sets, the WHERE clauses would be put in HAVING of the
subquery.

Then when we plan for the subquery, we will decide whether a HAVING
clause can be transfered into WHERE. Usually we do not do that if there
are any nonempty grouping sets. Because if any referenced column isn't
present in all the grouping sets, moving such a clause into WHERE would
potentially change the results.