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https://issues.apache.org/jira/browse/SPARK-60406?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated SPARK-60406:
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Labels: pull-request-available (was: )
> Count CollapseProject's column references by expression ID
> ----------------------------------------------------------
>
> Key: SPARK-60406
> URL: https://issues.apache.org/jira/browse/SPARK-60406
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 4.4.0
> Reporter: Anish Mahto
> Priority: Minor
> Labels: pull-request-available
>
> Count CollapseProject's references to a column by expression ID instead of by
> attribute equality.
> When two projections are adjacent, CollapseProject inlines each expression
> the lower one defines into the upper one's references to it. It does this
> only if the expression is referenced once, or is cheap enough to evaluate at
> every reference. Otherwise it keeps both projections, so the value is
> evaluated once and shared. References are counted by attribute equality,
> which includes the qualifier. So when one column is referenced both directly
> and through a subquery alias, its references are counted apart, and an
> expression referenced twice can count as once and be evaluated at each
> reference.
> Inlining itself finds references by expression ID, which identifies a column
> whatever its qualifier. Counting by expression ID therefore counts exactly
> the copies inlining will make. Only plans that reference one column under
> different qualifiers change.
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