[jira] Updated: (HIVE-439) merge small files after a map-only job

["Zheng Shao (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-439?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Zheng Shao updated HIVE-439:
----------------------------

    Affects Version/s: 0.3.1
                       0.3.0
        Fix Version/s: 0.4.0
              Summary: merge small files after a map-only job  (was: merge small files whenever possible)

> merge small files after a map-only job
> --------------------------------------
>
>                 Key: HIVE-439
>                 URL: https://issues.apache.org/jira/browse/HIVE-439
>             Project: Hadoop Hive
>          Issue Type: Improvement
>          Components: Query Processor
>    Affects Versions: 0.3.0, 0.3.1
>            Reporter: Namit Jain
>            Assignee: Namit Jain
>             Fix For: 0.4.0
>
>         Attachments: hive.439.1.patch, hive.439.2.patch, hive.439.3.patch, hive.439.4.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 these small files are combined into fewer larger files.
> The problem can also be addressed by having a mapper span multiple blocks as in:
> https://issues.apache.org/jira/browse/HIVE-74
> Bit, it also makes sense in HIVE to merge files whenever possible.

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