Whether the "partial aggregation push down" is already supported?

[bmmcq]

For example a query like this:

SELECT regionkey, count(*)
FROM nation
GROUP BY regionkey;

where the table "nation" has multiple sources and each source support aggregation push-down. So whether Trino supports pushing down partial aggregation to each source, and doing global aggregation itself, if the associative law and the commutative law are satisfied. e.g. the count operator in the example can be expressed as multiple partial counts and a global sum;