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https://issues.apache.org/jira/browse/IMPALA-9412?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Noemi Pap-Takacs reassigned IMPALA-9412:
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Assignee: Noemi Pap-Takacs
> Avoid unnecessary resource transfer from probe side to output for right semi
> joins
> ----------------------------------------------------------------------------------
>
> Key: IMPALA-9412
> URL: https://issues.apache.org/jira/browse/IMPALA-9412
> Project: IMPALA
> Issue Type: Improvement
> Components: Backend
> Reporter: Tim Armstrong
> Assignee: Noemi Pap-Takacs
> Priority: Trivial
> Labels: ramp-up
>
> In the join nodes, include NestedLoopJoinNode and PartitionedHashJoinNode, we
> transfer memory from the left child batches to the output, in case the output
> batch references the input data. This is not necessary for all join mode,
> e.g. RIGHT SEMI and RIGHT ANTI joins that only return row data from the right
> child. This results in unnecessary amounts of memory flowing up the plan
> tree. It's also a little undesirable in that it makes it unclear *why* the
> memory is transferred.
> E.g. see
> https://github.com/apache/impala/blob/0bb056e/be/src/exec/partitioned-hash-join-node.cc#L657
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