In this case, there is a function used in the query and materialized view, but the aggregate is not being pushed down. Script is attached.
Example query and materialized view:
create materialized view av1 stored as orc as select fk1, fk2, fk3, to_date(fk4), sum(1) from fact group by 1, 2, 3, 4;
explain cbo select pk1, dim2.fk4, sum(1), count(c1)
from fact, dim2
where to_date(fact.fk4) = dim2.fk4
group by 1, 2
order by 1, 2;