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https://issues.apache.org/jira/browse/SPARK-35439?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-35439:
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Assignee: L. C. Hsieh (was: Apache Spark)
> Use LinkedHashMap as the map of equivalent expressions to preserve insertion
> order
> ----------------------------------------------------------------------------------
>
> Key: SPARK-35439
> URL: https://issues.apache.org/jira/browse/SPARK-35439
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.0.2, 3.1.1, 3.2.0
> Reporter: L. C. Hsieh
> Assignee: L. C. Hsieh
> Priority: Minor
>
> EquivalentExpressions maintains a map of equivalent expressions. It is
> HashMap now so the insertion order is not guaranteed to be preserved later.
> Subexpression elimination relies on retrieving subexpressions from the map.
> If there is child-parent relationships among the subexpressions, we want the
> child expressions come first than parent expressions, so we can replace child
> expressions in parent expressions with subexpression evaluation.
> Although we add expressions recursively into the map with depth-first
> approach, when we retrieve the map values, it is not guaranteed that the
> order is preserved. We should use LinkedHashMap for this usage.
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