[HIVE-1783] CommonJoinOperator optimize the case of 1:1 join

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 0.7.0
• Hadoop Flags: Reviewed
• Assignee: Siying Dong
• Reporter: Siying Dong
• Created: 11/Nov/10 20:14
• Updated: 16/Dec/11 23:59
• Resolved: 19/Nov/10 00:12

Description

CommonJoinOperator.genObject() is expensive. It does a recursive and keeps lots of states because it has to:
1. handle null cases for outer joins
2. handle the case of duplicated keys from one join party
We can do a minor optimization to detect a 1:1 join (which is quite common) before calling CommonJoinOperator.genObject() and forward columns in a simple for-loop if we are sure neither of 1 or 2 will happen.