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Posted to issues-all@impala.apache.org by "bharath v (JIRA)" <ji...@apache.org> on 2019/03/28 05:29:00 UTC

[jira] [Assigned] (IMPALA-7637) Include more hash table stats in profile

     [ https://issues.apache.org/jira/browse/IMPALA-7637?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

bharath v reassigned IMPALA-7637:
---------------------------------

    Assignee: Yongzhi Chen

> Include more hash table stats in profile
> ----------------------------------------
>
>                 Key: IMPALA-7637
>                 URL: https://issues.apache.org/jira/browse/IMPALA-7637
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Backend
>            Reporter: Tim Armstrong
>            Assignee: Yongzhi Chen
>            Priority: Major
>              Labels: observability, ramp-up
>
> Our hash table collects some useful stats about collisions and travel length, but then we don't do anything to expose them: https://github.com/apache/impala/blob/540611e863fe99b3d3ae35f8b94a745a68b9eba2/be/src/exec/hash-table.h#L989
> We should add some of them to the profile, maybe:
> * the number of probes
> * the average travel length per probe
> * the number of hash collisions
> * (optional) the number of hash table resizes. We already have the hash table size and the resize time, which I think is sufficient to debug most problems with resizes.



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