Shant Hovsepian created IMPALA-10313:
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Summary: When inverting joins stats should be recomputed
Key: IMPALA-10313
URL: https://issues.apache.org/jira/browse/IMPALA-10313
Project: IMPALA
Issue Type: Improvement
Components: Frontend
Reporter: Shant Hovsepian
Assignee: Shant Hovsepian
Fix For: Impala 4.0
When searching a the cheapest join plan, a join may be inverted, this is safe
for certain join operators. While join equality is symmetric, foreign key and
primary key constraints are a directed relationship and therefore not always
symmetric. So when inverting a join we can simple just swap the cost and
cardinality for the left and right children as a change in order would affect
any estimated fk/pk cardinality.
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