[ https://issues.apache.org/jira/browse/HIVE-17043?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Vineet Garg updated HIVE-17043: ------------------------------- Status: Open (was: Patch Available) > Remove non unique columns from group by keys if not referenced later > -------------------------------------------------------------------- > > Key: HIVE-17043 > URL: https://issues.apache.org/jira/browse/HIVE-17043 > Project: Hive > Issue Type: Sub-task > Components: Logical Optimizer > Affects Versions: 3.0.0 > Reporter: Ashutosh Chauhan > Assignee: Vineet Garg > Priority: Major > Attachments: HIVE-17043.1.patch, HIVE-17043.2.patch, > HIVE-17043.3.patch > > > Group by keys may be a mix of unique (or primary) keys and regular columns. > In such cases presence of regular column won't alter cardinality of groups. > So, if regular columns are not referenced later, they can be dropped from > group by keys. Depending on operator tree may result in those columns not > being read at all from disk in best case. In worst case, we will avoid > shuffling and sorting regular columns from mapper to reducer, which still > could be substantial CPU and network savings. -- This message was sent by Atlassian JIRA (v7.6.3#76005)