[ https://issues.apache.org/jira/browse/HIVE-21387?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Vineet Garg reassigned HIVE-21387: ---------------------------------- > Wrong result for UNION query with GROUP BY consisting of PK columns > ------------------------------------------------------------------- > > Key: HIVE-21387 > URL: https://issues.apache.org/jira/browse/HIVE-21387 > Project: Hive > Issue Type: Bug > Components: Query Planning > Affects Versions: 4.0.0 > Reporter: Vineet Garg > Assignee: Vineet Garg > Priority: Major > > *Reproducer* > {code:sql} > create table t1(i int primary key disable rely, j int); > insert into t1 values(1,100),(2,200); > create table t2(i int primary key disable rely, j int); > insert into t2 values(2,1000),(4,500); > select i from (select i, j from t1 union all select i,j from t2) subq group > by i,j; > {code} > *Expected Result* > {noformat} > 2 > 2 > 4 > 1 > {noformat} > *Actual Result* > {noformat} > 1 > 2 > 4 > {noformat} > *CBO Plan* > {code:sql} > HiveAggregate(group=[{0}]) > HiveProject(i=[$0], j=[$1]) > HiveUnion(all=[true]) > HiveProject(i=[$0], j=[$1]) > HiveTableScan(table=[[default, t1]], table:alias=[t1]) > HiveProject(i=[$0], j=[$1]) > HiveTableScan(table=[[default, t2]], table:alias=[t2]) > {code} > This is due to Group by reduction logic reducing keys when it shouldn't. > Because of UNION relative cardinality of the group by keys are changed (they > are not PK/UNIQUE anymore). Therefore we shouldn't be trying to reduce group > by keys at all. -- This message was sent by Atlassian JIRA (v7.6.3#76005)