set hive.stats.autogather=false; set hive.optimize.union.remove=true; set hive.mapred.supports.subdirectories=true; set hive.merge.sparkfiles=true; set hive.merge.mapfiles=true; set hive.merge.mapredfiles=true; set hive.merge.smallfiles.avgsize=1; set mapred.input.dir.recursive=true; -- This is to test the union->selectstar->filesink optimization -- Union of 2 subqueries is performed (one of which is a map-only query, and the -- other one contains a nested union where one of the sub-queries requires a map-reduce -- job), 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 outer union can be removed completely. -- The final file format is different from the input and intermediate file format. -- It does not matter, whether the output is merged or not. In this case, merging is turned -- on -- 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 create table inputTbl1(key string, val string) stored as textfile; create table outputTbl1(key string, `values` bigint) stored as rcfile; load data local inpath '../../data/files/T1.txt' into table inputTbl1; explain insert overwrite table outputTbl1 SELECT * FROM ( select key, 1 as `values` from inputTbl1 union all select * FROM ( SELECT key, count(1) as `values` from inputTbl1 group by key UNION ALL SELECT key, 2 as `values` from inputTbl1 ) a )b; insert overwrite table outputTbl1 SELECT * FROM ( select key, 1 as `values` from inputTbl1 union all select * FROM ( SELECT key, count(1) as `values` from inputTbl1 group by key UNION ALL SELECT key, 2 as `values` from inputTbl1 ) a )b; desc formatted outputTbl1; set hive.input.format=org.apache.hadoop.hive.ql.io.HiveInputFormat; select * from outputTbl1 order by key, `values`;