[ https://issues.apache.org/jira/browse/HIVE-1772?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Navis updated HIVE-1772: ------------------------ Attachment: HIVE-1772.1.patch initial patch.. dependent to HIVE-2339 > optimize join followed by a groupby > ----------------------------------- > > Key: HIVE-1772 > URL: https://issues.apache.org/jira/browse/HIVE-1772 > Project: Hive > Issue Type: Improvement > Components: Query Processor > Reporter: Namit Jain > Attachments: HIVE-1772.1.patch > > > explain SELECT x.key, count(1) FROM src1 x JOIN src y ON (x.key = y.key) > group by x.key; > STAGE DEPENDENCIES: > Stage-1 is a root stage > Stage-2 depends on stages: Stage-1 > Stage-0 is a root stage > The above query issues 2 map-reduce jobs. > The first MR job performs the join, whereas the second MR performs the group > by. > Since the data is already sorted, the group by can be performed in the > reducer of the join itself. -- This message is automatically generated by JIRA. For more information on JIRA, see: http://www.atlassian.com/software/jira