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Posted to issues-all@impala.apache.org by "Quanlong Huang (Jira)" <ji...@apache.org> on 2021/07/12 14:12:00 UTC

[jira] [Updated] (IMPALA-10313) When inverting joins stats should be recomputed

     [ https://issues.apache.org/jira/browse/IMPALA-10313?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Quanlong Huang updated IMPALA-10313:
------------------------------------
    Fix Version/s:     (was: Impala 4.0)

> 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
>            Priority: Major
>
> 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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