MM tables - many queries duplicate the data after master merge

Update: happens on many more queries it looks like, and started happening after a recent master merge after I wasn't working on the feature for a while

This duplicates the data (given that the original query is a self-union, essentially outputs it 4 times instead of 2) for either MM or non-MM tables, on MM branch.

It seems to be adding correct inputs (esp. in non-MM case the inputs are the same as before). Presumably something in the output changes in the branch is broken for this case. Not sure what yet.

CREATE TABLE tbl1_mm(key int, value string) CLUSTERED BY (key) SORTED BY (key) INTO 2 BUCKETS;
insert overwrite table tbl1_mm select * from src where key < 10;

select key, value from tbl1_mm a where key < 6
union all
select key, value from tbl1_mm a where key < 6;