[ https://issues.apache.org/jira/browse/HIVE-3598?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13479310#comment-13479310 ]
Namit Jain commented on HIVE-3598: ---------------------------------- After HIVE-3403, an auto sortmerge join can be performed. However, consider the following scenario: T1 - big table: 3 partitions : big partitions T2 - small table: 1 partition both T1 and T2 are sorted/bucketed on the same key. If a join is being performed between T1 and T2, with HIVE-3403, T2 would be picked up as the table on which the mapper would run. Ideally, if T2 is so small that it can fit in memory, a better approach would be map-join. The physical optimizer should change the sort-merge join task into a backup task, with all tables being candidates for map-join (similar to auto convert mapjoin). > physical optimizer changes for auto sort-merge join > --------------------------------------------------- > > Key: HIVE-3598 > URL: https://issues.apache.org/jira/browse/HIVE-3598 > Project: Hive > Issue Type: Bug > Reporter: Namit Jain > -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira