[jira] [Assigned] (HIVE-12310) Update memory estimation login in TopNHash

["Hari Sankar Sivarama Subramaniyan (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-12310?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hari Sankar Sivarama Subramaniyan reassigned HIVE-12310:
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    Assignee: Hari Sankar Sivarama Subramaniyan

> Update memory estimation login in TopNHash
> ------------------------------------------
>
>                 Key: HIVE-12310
>                 URL: https://issues.apache.org/jira/browse/HIVE-12310
>             Project: Hive
>          Issue Type: Bug
>          Components: Query Processor
>            Reporter: Thejas M Nair
>            Assignee: Hari Sankar Sivarama Subramaniyan
>
> HIVE-12084 changes TopNHash to use Runtime.getRuntime().freeMemory() for finding available memory.
> However, it does not give the all the memory it could use, it ignores unallocated memory. This is because the heap size of jvm grows up to max heap size (-Xmx) as per it needs. totalMemory() gives total heap space it has allocated, and freeMemory() is the free memory within that.
> See http://i.stack.imgur.com/GjuwM.png and http://stackoverflow.com/questions/3571203/what-is-the-exact-meaning-of-runtime-getruntime-totalmemory-and-freememory .
> So instead of using Runtime.getRuntime().freeMemory() , I think it should use maxMemory() - totalMemory() + freeMemory()



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