[jira] Commented: (HIVE-74) Hive can use CombineFileInputFormat for when the input are many small files

["Raghotham Murthy (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-74?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12753791#action_12753791 ] 

Raghotham Murthy commented on HIVE-74:
--------------------------------------

Why does Hadoop18Shims.java have 
{code}
+    return "org.apache.hadoop.hive.ql.io.CombineHiveInputFormat";
{code}

> 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: 0.4.0
>
>         Attachments: hive.74.1.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

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