Convert Inner Join With Aggregate To Semi Join

Inner Join with aggregation on one of its child it equivalent to a Semi Join with the aggregation eliminated If the aggregation is just doing grouping and all the grouping columns appears in the join condition.

For example, Inner Join like below

select * from table1 inner join (select key2 from table2 group by key2) subquery on table1.key1 = subquery.key2

can be transformed to a semi join and eliminate the aggregate in the subquery

select * from table1 semi join (select key2 from table2) subquery on table1.key1 = subquery.key2

I think this can be added as a optimize rule to save the unnecessary aggregation in the subquery.