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From "Dong Chen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-7685) Parquet memory manager
Date Mon, 29 Sep 2014 08:44:33 GMT

    [ https://issues.apache.org/jira/browse/HIVE-7685?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14151496#comment-14151496
] 

Dong Chen commented on HIVE-7685:
---------------------------------

Hi Brock,

I think a brief design for this memory manager is:
Every new writer registers itself to the manager. The manager has an overall view of all the
writers. When a condition is up (such as every 1000 rows), it will notify the writers to check
memory usage and flush if necessary.

However, a problem for Parquet specifically is: Hive only has a wrapper for the ParquetRecordWriter,
and even ParquetRecordWriter also wrap the real writer (InternalParquetRecordWriter) in Parquet
project. Since the behaviors of measuring dynamic buffer size and flushing are private in
the real writer, I think we also have to add code in InternalParquetRecordWriter to implement
the memory manager functionality. 

It seems only changing Hive code cannot fix this Jira. 
Not sure whether we should put this problem in Parquet project and fix it there, if it is
generic enough and not Hive specific? 

Any other ideas?

Best Regards,
Dong

> Parquet memory manager
> ----------------------
>
>                 Key: HIVE-7685
>                 URL: https://issues.apache.org/jira/browse/HIVE-7685
>             Project: Hive
>          Issue Type: Improvement
>          Components: Serializers/Deserializers
>            Reporter: Brock Noland
>
> Similar to HIVE-4248, Parquet tries to write large very large "row groups". This causes
Hive to run out of memory during dynamic partitions when a reducer may have many Parquet files
open at a given time.
> As such, we should implement a memory manager which ensures that we don't run out of
memory due to writing too many row groups within a single JVM.



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