[jira] [Assigned] (IMPALA-13660) Cache broadcast hash joins

["Michael Smith (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-13660?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Michael Smith reassigned IMPALA-13660:
--------------------------------------

    Assignee: Michael Smith

> Cache broadcast hash joins
> --------------------------
>
>                 Key: IMPALA-13660
>                 URL: https://issues.apache.org/jira/browse/IMPALA-13660
>             Project: IMPALA
>          Issue Type: Improvement
>            Reporter: Michael Smith
>            Assignee: Michael Smith
>            Priority: Major
>
> Enable intermediate result caching for broadcast hash joins. The cache key must incorporate probe and build sides; since the build side will be part of the cache key, we can rely on the broadcast results being stable.
> This differs from a partition join, where we don't have the same guarantees; partition joins would also incorporate an exchange on the probe side, so our normal rules would preclude caching it right now.
> The build side comes from another fragment, so we need to tolerate an exchange on the build side, similar to what was done in IMPALA-13185.
> We need to make sure cached results are returned immediately when available rather than waiting on a build side we don't need; also make sure the build side can complete even if its results are not needed by any joins (because they all had cache hits). It would be nice to cancel the build side fragment if a cache hit is identified on all join fragments, since the build side results would no longer be needed.



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