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Posted to issues-all@impala.apache.org by "Tim Armstrong (JIRA)" <ji...@apache.org> on 2018/10/23 21:34:00 UTC
[jira] [Updated] (IMPALA-6178) Heuristic for selecting the
left-most table should consider parallelism.
[ https://issues.apache.org/jira/browse/IMPALA-6178?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Tim Armstrong updated IMPALA-6178:
----------------------------------
Target Version: Product Backlog
> 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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