[SPARK-9258] Remove all semi join physical operator

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Component/s: SQL
• Epic Link: Tungsten Phase 1
• Assignee: Unassigned
• Reporter: Reynold Xin
• Created: 22/Jul/15 18:54
• Updated: 06/Aug/15 18:33
• Resolved: 06/Aug/15 18:33

Description

We have 4 semi join operators. In this case, they are not very very necessary. We can still use an equi-join operator to do the join, and just not include any values from the other join.

We waste a little bit space due to building a hash map rather than a hash set, but at the end of the day unless we are going to spend a lot of time optimizing hash set, our Tungsten hash map will be a lot more efficient than the hash set anyway. This way, semi-join automatically benefits from all the work we do in Tungsten.