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https://issues.apache.org/jira/browse/IMPALA-6178?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tim Armstrong resolved IMPALA-6178.
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Resolution: Later
I think this is a little vague. We can come back to it later if needed.
> Heuristic for selecting the left-most table should consider parallelism.
> ------------------------------------------------------------------------
>
> Key: IMPALA-6178
> URL: https://issues.apache.org/jira/browse/IMPALA-6178
> Project: IMPALA
> Issue Type: Improvement
> Components: Frontend
> Affects Versions: Impala 2.10.0, Impala 2.11.0
> Reporter: Alexander Behm
> Priority: Major
> Labels: performance, planner
>
> For each query block, Impala uses the estimated materialized size of tables
> as a heuristic for choosing the left-most table in a series of joins.
> Unfortunately, that heuristic does not factor in the number of hosts that
> tables will execute on. The number of hosts of the left-most table dictates
> the degree of inter-node parallelism.
> To handle this tradeoff between parallelism and size we should use a
> heuristic like the one in IMPALA-5612.
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