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From "Sergey Shelukhin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-16329) TopN: TopNHash totalFreeMemory computation ignores free memory
Date Thu, 30 Mar 2017 18:27:41 GMT

    [ https://issues.apache.org/jira/browse/HIVE-16329?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15949551#comment-15949551
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Sergey Shelukhin commented on HIVE-16329:
-----------------------------------------

On the patch itself - where isLlap flag is used, should it access it via the LlapDaemonInfo
static, and not from wherever it get this now?

> TopN: TopNHash totalFreeMemory computation ignores free memory
> --------------------------------------------------------------
>
>                 Key: HIVE-16329
>                 URL: https://issues.apache.org/jira/browse/HIVE-16329
>             Project: Hive
>          Issue Type: Bug
>    Affects Versions: 2.2.0, 3.0.0
>            Reporter: Gopal V
>            Assignee: Gopal V
>         Attachments: HIVE-16329.1.patch
>
>
> {code}
>       // TODO: For LLAP, assumption is off-heap cache.
>       final long memoryUsedPerExecutor = (memoryMXBean.getHeapMemoryUsage().getUsed()
/ numExecutors);
>       // this is total free memory available per executor in case of LLAP
>       totalFreeMemory = conf.getMaxMemoryAvailable() - memoryUsedPerExecutor;
> {code}
> {code}
> exec.TopNHash: isTez parameters -615768144 = 5312782848 - 71142611912 / 12
> {code}
> This turns off the TopNHash entirely causing something trivial like 
> {code}
> select c_custkey, count(1) from customer group by c_custkey limit 10;
> {code}
> To shuffle 30M rows instead of 10.



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