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  1. IMPALA
  2. IMPALA-10313

When inverting joins stats should be recomputed

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    • Improvement
    • Status: Open
    • Major
    • Resolution: Unresolved
    • None
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    • ghx-label-4

    Description

      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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            superdupershant Shant Hovsepian
            superdupershant Shant Hovsepian
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              Created:
              Updated: