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https://issues.apache.org/jira/browse/SPARK-37341?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-37341:
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Assignee: Apache Spark
> Avoid unnecessary buffer and copy in full outer sort merge join
> ---------------------------------------------------------------
>
> Key: SPARK-37341
> URL: https://issues.apache.org/jira/browse/SPARK-37341
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.3.0
> Reporter: Cheng Su
> Assignee: Apache Spark
> Priority: Minor
>
> FULL OUTER sort merge join (non-code-gen path) copies join keys and buffers
> input rows, even when rows from both sides do have matched keys
> ([https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/joins/SortMergeJoinExec.scala#L1637-L1641]
> ). This is unnecessary, as we can just output the row with smaller join
> keys, and only buffer when both sides have matched keys. This would save us
> from unnecessary copy and buffer, when both join sides have a lot of rows not
> matched with each other.
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