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From Yongqiang He <>
Subject Re: merging the size of the reduce output
Date Mon, 14 Jun 2010 05:55:31 GMT
I think there is another parameter ³hive.merge.smallfiles.avgsize²  to see
whether to do the merge job or not based on the average output files¹ size.
The default for that parameter is 16M. So if the average output¹s size is
larger than 16M, will not merge.
Maybe you can try to increase that value to see.

On 6/13/10 10:41 PM, "Sammy Yu" <> wrote:

> Hi,
>    I have both hive.merge.mapredfiles and hive.merge.mapredfiles set to true
> via the shell tool and hive-default.xml configuration file.  However, it
> appears somehow the job configuration is changed before the job is submitted.
>  Is there another condition that can cause this to happen?
> Thanks,
> Sammy
> On Sun, Jun 13, 2010 at 7:39 AM, Ted Yu <> wrote:
>> Looking at 
>> ql/src/java/org/apache/hadoop/hive/ql/optimizer/,
>> hive.merge.mapredfiles is effective if there is a reducer for your job.
>> Otherwise you should have set hive.merge.mapfiles to true.
>> On Sat, Jun 12, 2010 at 11:22 PM, Sammy Yu <> wrote:
>>> Hi, 
>>>    I'm running the latest version of trunk r953172.  I'm doing doing a
>>> dynamic partition insert overwrite query which generates a lot of small
>>> files in each of the partition.  I was hoping this could be solved by
>>> setting hive.merge.mapredfiles to true.  However, it seems like whenever the
>>> job is submitted it is always set to false, thus it doesnt seem to have any
>>> effect.  I also tried to modified this property in the hive-default.xml, but
>>> it didn't work either. 
>>> Thanks,
>>> Sammy

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