[PHOENIX-5793] Support parallel init and fast null return for SortMergeJoinPlan.

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 5.0.0
• Fix Version/s: 5.1.0, 4.16.0
• Assignee: Chen Feng
• Reporter: Chen Feng
• Created: 23/Mar/20 12:09
• Updated: 22/Jun/20 11:54
• Resolved: 20/Jun/20 08:13

Description

For a join sql like A join B. The implementation of SortMergeJoinPlan currently inits the two iterators A and B one by one.

By initializing A and B in parallel, we can improve performance in two aspects.

1) By overlapping the time in initializing.

2) If one child query is null, the other child query can be canceled since the final result must be null.