Details
-
Improvement
-
Status: Closed
-
Major
-
Resolution: Fixed
-
None
-
None
Description
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:
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
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.
Attachments
Issue Links
- links to
