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Date: Wed, 21 Oct 2009 11:29:59 +0000 (UTC)
From: "Zheng Shao (JIRA)" <jira@apache.org>
To: hive-dev@hadoop.apache.org
Subject: [jira] Updated: (HIVE-74) Hive can use CombineFileInputFormat for
 when the input are many small files
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     [ https://issues.apache.org/jira/browse/HIVE-74?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Zheng Shao updated HIVE-74:
---------------------------

    Description: 
There are cases when the input to a Hive job are thousands of small files. In this case, there is a mapper for each file. Most of the overhead for spawning all these mappers can be avoided if Hive used CombineFileInputFormat introduced via HADOOP-4565


Options to control this behavior:

{code}
hive.input.format (org.apache.hadoop.hive.ql.io.CombineHiveInputFormat (default, if empty), or org.apache.hadoop.hive.ql.io.HiveInputFormat)
mapred.min.split.size.per.node (the minimum bytes of data to create a node-local partition, otherwise the data will combine to rack level. default:0)
mapred.min.split.size.per.rack (the minimum bytes of data to create a rack-local partition, otherwise the data will combine to global level. default:0)
mapred.max.split.size (the max size of each split, will be exceeded because we stop accumulating *after* reaching it, instead of before)
{code}

The 3 numbers above must be in non-descending order.


  was:There are cases when the input to a Hive job are thousands of small files. In this case, there is a mapper for each file. Most of the overhead for spawning all these mappers can be avoided if Hive used CombineFileInputFormat introduced via HADOOP-4565


> Hive can use CombineFileInputFormat for when the input are many small files
> ---------------------------------------------------------------------------
>
>                 Key: HIVE-74
>                 URL: https://issues.apache.org/jira/browse/HIVE-74
>             Project: Hadoop Hive
>          Issue Type: Improvement
>          Components: Query Processor
>            Reporter: dhruba borthakur
>            Assignee: Namit Jain
>             Fix For: 0.5.0
>
>         Attachments: hive.74.1.patch, hive.74.2.patch, hiveCombineSplit.patch, hiveCombineSplit.patch, hiveCombineSplit2.patch
>
>
> There are cases when the input to a Hive job are thousands of small files. In this case, there is a mapper for each file. Most of the overhead for spawning all these mappers can be avoided if Hive used CombineFileInputFormat introduced via HADOOP-4565
> Options to control this behavior:
> {code}
> hive.input.format (org.apache.hadoop.hive.ql.io.CombineHiveInputFormat (default, if empty), or org.apache.hadoop.hive.ql.io.HiveInputFormat)
> mapred.min.split.size.per.node (the minimum bytes of data to create a node-local partition, otherwise the data will combine to rack level. default:0)
> mapred.min.split.size.per.rack (the minimum bytes of data to create a rack-local partition, otherwise the data will combine to global level. default:0)
> mapred.max.split.size (the max size of each split, will be exceeded because we stop accumulating *after* reaching it, instead of before)
> {code}
> The 3 numbers above must be in non-descending order.

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