[TAJO-903] Some left outer join cases are not optimized as the broadcast join.

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.9.0
• Assignee: Hyoungjun Kim
• Reporter: Hyoungjun Kim
• Created: 03/Jul/14 18:33
• Updated: 09/Jul/14 09:53
• Resolved: 09/Jul/14 09:43

Description

The next query has three small tables and expected broadcast join, but not.

select count(*) from large1 
left outer join large2 on large1_id = large2_id
left outer join small1 on large1_id = small1_id
left outer join small2 on large1_id = small2_id
left outer join small3 on large1_id = small3_id

The next is the upper query's plan.

|-eb_1404411535695_0000_000011
   |-eb_1404411535695_0000_000010
      |-eb_1404411535695_0000_000009 (join)
         |-eb_1404411535695_0000_000008 (small)
         |-eb_1404411535695_0000_000007 (join)
            |-eb_1404411535695_0000_000006 (small)
            |-eb_1404411535695_0000_000005 (join)
               |-eb_1404411535695_0000_000004 (small)
               |-eb_1404411535695_0000_000003 (join)
                  |-eb_1404411535695_0000_000002 (large)
                  |-eb_1404411535695_0000_000001 (large)

Optimized plan should be the next.

|-eb_1404411906426_0000_000005
   |-eb_1404411906426_0000_000004
      |-eb_1404411906426_0000_000003 (broadcast small1, small2, small3)
         |-eb_1404411906426_0000_000002 (large)
         |-eb_1404411906426_0000_000001 (large)