set hive.map.aggr = true;

-- SORT_QUERY_RESULTS

-- union case: both subqueries are map-reduce jobs on same input, followed by filesink


create table tmptable(key string, value int);

explain 
insert overwrite table tmptable
  select unionsrc.key, unionsrc.value FROM (select 'tst1' as key, count(1) as value from src s1
                                        UNION  ALL  
                                            select 'tst2' as key, count(1) as value from src s2) unionsrc;

insert overwrite table tmptable
select unionsrc.key, unionsrc.value FROM (select 'tst1' as key, count(1) as value from src s1
                                        UNION  ALL  
                                          select 'tst2' as key, count(1) as value from src s2) unionsrc;

select * from tmptable x sort by x.key;