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https://issues.apache.org/jira/browse/IMPALA-14745?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Steve Carlin updated IMPALA-14745:
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Epic Link: IMPALA-15133
> Calcite planner: Join optimizer should factor in parallelism of nodes
> ---------------------------------------------------------------------
>
> Key: IMPALA-14745
> URL: https://issues.apache.org/jira/browse/IMPALA-14745
> Project: IMPALA
> Issue Type: Bug
> Reporter: Steve Carlin
> Priority: Major
>
> Comment from join optimization code review of
> [https://gerrit.cloudera.org/#/c/23924/6/java/calcite-planner/src/main/java/org/apache/impala/calcite/rules/ImpalaLoptOptimizeJoinRule.java@1930]
> One of the things that Impala's Planner.isInvertedJoinsCheaper() [1]
> considers is the parallelism (besides the cost). There are situations where
> if you only make the decision based on cost, the probe side can end up with
> much lower parallelism than without swapping and this adversely affects
> performance because the HashJoin node's parallelism depends on the left
> input's (probe) parallelism. Is the numNodes value available at this stage in
> the Calcite planning for the left and right child ? If so, it would be useful
> to incorporate. Whether in this patch or an enhancement.
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