[ https://issues.apache.org/jira/browse/TRAFODION-2418?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Hans Zeller closed TRAFODION-2418. ---------------------------------- > Allow group by push-down to a fact table > ---------------------------------------- > > Key: TRAFODION-2418 > URL: https://issues.apache.org/jira/browse/TRAFODION-2418 > Project: Apache Trafodion > Issue Type: Improvement > Components: sql-cmp > Reporter: Hans Zeller > Assignee: Hans Zeller > Fix For: 2.1-incubating > > > Trafodion has a rule that pushes a groupby down over a join when possible, > but it will not push the groupby to the left child of a join - it relies on > join commutativity. This might have been ok 20 years ago when this was coded > (by me...), but it isn't good for some situations today. Example: > {noformat} > select d.y, count(f.a), sum(f.b) > from big_fact f join small_dim d on f.x=d.y > where d.a = 1 > group by d.y > {noformat} > The plan we would like is a hash join with the group by on big_fact as the > left child. To do this, we need to remove the heuristic that prevents this > form of push-down. -- This message was sent by Atlassian JIRA (v6.3.4#6332)