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From "Gunther Hagleitner (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-15565) LLAP: GroupByOperator flushes hash table too frequently
Date Mon, 16 Jan 2017 22:01:26 GMT

    [ https://issues.apache.org/jira/browse/HIVE-15565?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15824647#comment-15824647
] 

Gunther Hagleitner commented on HIVE-15565:
-------------------------------------------

I don't understand this - isn't the commit doing the exact opposite of what [~prasanth_j]
says? This is flushing when the JVM memory is hit v the max allocated memory per executor.
This would have a lot of bad side effects by having multiple queries/fragments step on one
another...

> LLAP: GroupByOperator flushes hash table too frequently
> -------------------------------------------------------
>
>                 Key: HIVE-15565
>                 URL: https://issues.apache.org/jira/browse/HIVE-15565
>             Project: Hive
>          Issue Type: Bug
>          Components: llap
>            Reporter: Rajesh Balamohan
>            Assignee: Rajesh Balamohan
>            Priority: Minor
>             Fix For: 2.2.0
>
>         Attachments: HIVE-15565.1.patch
>
>
> {{GroupByOperator::isTez}} would be true in LLAP mode. Current memory computations can
go wrong with {{isTez}} checks in {{GroupByOperator}}. For e.g, in a LLAP instance with Xmx128G
and 12 executors, it would start flushing hash table for every record once it reaches around
42GB (hive.tez.container.size=7100, hive.map.aggr.hash.percentmemory=0.5).
> {noformat}
> 2017-01-08T23:40:21,339 INFO  [TezTaskRunner (1480722417364_1922_7_03_000004_1)] org.apache.hadoop.hive.ql.exec.GroupByOperator:
Hash Table flushed: new size = 0
> 2017-01-08T23:40:21,339 INFO  [TezTaskRunner (1480722417364_1922_7_03_000012_1)] org.apache.hadoop.hive.ql.exec.GroupByOperator:
Hash Table flushed: new size = 0
> 2017-01-08T23:40:21,339 INFO  [TezTaskRunner (1480722417364_1922_7_03_000004_1)] org.apache.hadoop.hive.ql.exec.GroupByOperator:
Hash Tbl flush: #hash table = 1
> 2017-01-08T23:40:21,339 INFO  [TezTaskRunner (1480722417364_1922_7_03_000012_1)] org.apache.hadoop.hive.ql.exec.GroupByOperator:
Hash Tbl flush: #hash table = 1
> {noformat}



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