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From "Gajendran, Vishnu" <vis...@amazon.com>
Subject RE: hive 13: dynamic partition inserts
Date Tue, 22 Jul 2014 18:47:33 GMT
Hi Prasanth,

 Thanks a lot for your quick response.
________________________________
From: Prasanth Jayachandran [pjayachandran@hortonworks.com]
Sent: Tuesday, July 22, 2014 11:28 AM
To: user@hive.apache.org
Cc: dev@hive.apache.org
Subject: Re: hive 13: dynamic partition inserts

Hi Vishnu

Yes. There is change in the way dynamic partitions are inserted in hive 13. The new dynamic
partitioning is highly scalable and uses very less memory. Here is the related JIRA  https://issues.apache.org/jira/browse/HIVE-6455.

Setting "hive.optimize.sort.dynamic.partition" to false will fallback to old way of insertion.
If your destination table uses columnar formats like ORC, Parquet etc. then it makes sense
leave the optimization ON, as columnar formats needs some buffer space for each column before
flushing to disk. Buffer space (runtime memory) will quickly shoot up when there are lots
of partition column values and columns. HIVE-6455 addresses this issue.

Thanks
Prasanth Jayachandran

On Jul 22, 2014, at 10:51 AM, Gajendran, Vishnu <vishng@amazon.com<mailto:vishng@amazon.com>>
wrote:

adding user@hive.apache.org<mailto:user@hive.apache.org> for wider audience
________________________________
From: Gajendran, Vishnu
Sent: Tuesday, July 22, 2014 10:42 AM
To: dev@hive.apache.org<mailto:dev@hive.apache.org>
Subject: hive 13: dynamic partition inserts

Hello,

I am seeing a difference between hive 11 and hive 13 when inserting to a table with dynamic
partitions.

In Hive 11, when I set hive.merge.mapfiles=false before doing a dynamic partition insert,
I see number of files (generated my each mapper) in the specified hdfs location as expected.
But, in Hive 13, when I set hive.merge.mapfiles=false, I just see one file in specified hdfs
location for the same query. I think hive is not honoring the hive.merge.mapfiles parameter
and it merged all the mapper outputs to a single file.

In Hive 11, 19 mappers were executed for the dynamic partition insert task. But in Hive 13,
19 mappers and 2 reducers were executed.

When I checked the query plan for hive 11, there is only a map operator task for dynamic partition
insert. But, in hive 13, I see both map operator and reduce operator task.

Is there any changes in hive 13 regarding dymamic partition inserts? Any comments on this
issue is greatly appreciated.

Thanks,
vishnu


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