Xiao Li created SPARK-12613:
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Summary: Elimination of Outer Join by Parent Join Condition
Key: SPARK-12613
URL: https://issues.apache.org/jira/browse/SPARK-12613
Project: Spark
Issue Type: Improvement
Components: SQL
Affects Versions: 1.6.0
Reporter: Xiao Li
Priority: Critical
Given an outer join is involved in another join (called parent join), when the
join type of the parent join is inner, left-semi, left-outer and right-outer,
checking if the join condition of the parent join satisfies the following two
conditions:
1) there exist null filtering predicates against the columns in the
null-supplying side of parent join.
2) these columns are from the child join.
If having such join predicates, execute the elimination rules:
- full outer -> inner if both sides of the child join have such predicates
- left outer -> inner if the right side of the child join has such predicates
- right outer -> inner if the left side of the child join has such predicates
- full outer -> left outer if only the left side of the child join has such
predicates
- full outer -> right outer if only the right side of the child join has such
predicates
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