Tim Armstrong created IMPALA-9412:
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Summary: 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
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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