[jira] [Commented] (HIVE-20656) Sensible defaults: Map aggregation memory configs are too aggressive

["Prasanth Jayachandran (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-20656?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16785157#comment-16785157 ] 

Prasanth Jayachandran commented on HIVE-20656:
----------------------------------------------

Golden files updated. 

> Sensible defaults: Map aggregation memory configs are too aggressive
> --------------------------------------------------------------------
>
>                 Key: HIVE-20656
>                 URL: https://issues.apache.org/jira/browse/HIVE-20656
>             Project: Hive
>          Issue Type: Bug
>    Affects Versions: 4.0.0, 3.2.0
>            Reporter: Prasanth Jayachandran
>            Assignee: Prasanth Jayachandran
>            Priority: Major
>         Attachments: HIVE-20656.1.patch, HIVE-20656.2.patch
>
>
> The defaults for the following configs seems to be too aggressive. In java this can easily lead to several full GC pauses whose memory cannot be reclaimed.
> {code:java}
> HIVEMAPAGGRHASHMEMORY("hive.map.aggr.hash.percentmemory", (float) 0.99,
>     "Portion of total memory to be used by map-side group aggregation hash table"),
> HIVEMAPAGGRMEMORYTHRESHOLD("hive.map.aggr.hash.force.flush.memory.threshold", (float) 0.9,
>     "The max memory to be used by map-side group aggregation hash table.\n" +
>     "If the memory usage is higher than this number, force to flush data"),{code}
>  
> We can be little bit conservative for these configs to avoid getting into GC pause. 



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