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https://issues.apache.org/jira/browse/IMPALA-7637?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yongzhi Chen resolved IMPALA-7637.
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Fix Version/s: Impala 3.4.0
Resolution: Fixed
> 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
> Fix For: Impala 3.4.0
>
>
> 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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