set hive.stats.autogather=false; set hive.optimize.union.remove=true; set hive.mapred.supports.subdirectories=true; set hive.merge.sparkfiles=false; set hive.merge.mapfiles=false; set hive.merge.mapredfiles=false; set mapred.input.dir.recursive=true; -- This is to test the union->selectstar->filesink optimization -- Union of 2 map-reduce subqueries is performed followed by select star and a file sink -- There is no need to write the temporary results of the sub-queries, and then read them -- again to process the union. The union can be removed completely. -- It does not matter, whether the output is merged or not. In this case, merging is turned -- off -- INCLUDE_HADOOP_MAJOR_VERSIONS(0.23) -- Since this test creates sub-directories for the output table outputTbl1, it might be easier -- to run the test only on hadoop 23 -- SORT_QUERY_RESULTS create table inputTbl1(key string, val string) stored as textfile; create table outputTbl1(key string, `values` bigint) stored as textfile; load data local inpath '../../data/files/T1.txt' into table inputTbl1; explain insert overwrite table outputTbl1 SELECT a.key, a.`values` FROM ( SELECT key, count(1) as `values` from inputTbl1 group by key UNION ALL SELECT key, count(1) as `values` from inputTbl1 group by key ) a; insert overwrite table outputTbl1 SELECT a.key, a.`values` FROM ( SELECT key, count(1) as `values` from inputTbl1 group by key UNION ALL SELECT key, count(1) as `values` from inputTbl1 group by key ) a; desc formatted outputTbl1; select * from outputTbl1; -- filter should be fine explain insert overwrite table outputTbl1 SELECT a.key, a.`values` FROM ( SELECT key, count(1) as `values` from inputTbl1 group by key UNION ALL SELECT key, count(1) as `values` from inputTbl1 group by key ) a where a.key = 7; insert overwrite table outputTbl1 SELECT a.key, a.`values` FROM ( SELECT key, count(1) as `values` from inputTbl1 group by key UNION ALL SELECT key, count(1) as `values` from inputTbl1 group by key ) a where a.key = 7; select * from outputTbl1; -- filters and sub-queries should be fine explain insert overwrite table outputTbl1 select key, `values` from ( SELECT a.key + a.key as key, a.`values` FROM ( SELECT key, count(1) as `values` from inputTbl1 group by key UNION ALL SELECT key, count(1) as `values` from inputTbl1 group by key ) a ) b where b.key >= 7; insert overwrite table outputTbl1 select key, `values` from ( SELECT a.key + a.key as key, a.`values` FROM ( SELECT key, count(1) as `values` from inputTbl1 group by key UNION ALL SELECT key, count(1) as `values` from inputTbl1 group by key ) a ) b where b.key >= 7; set hive.input.format=org.apache.hadoop.hive.ql.io.HiveInputFormat; select * from outputTbl1 order by key, `values`;