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From "Namit Jain (JIRA)" <>
Subject [jira] Commented: (HIVE-439) merge small files whenever possible
Date Fri, 19 Jun 2009 06:11:07 GMT


Namit Jain commented on HIVE-439:

It does not - ConditionalTask is executed on the client side i.e Hive server.
The resolver and resolver can be accessed there - no seriaiization required - 
it is not a map-reduce task.

It is just a placeholder to decide which task to execute. Since this decision cannot be made
compile time, and must be made after certain tasks are executed

> merge small files whenever possible
> -----------------------------------
>                 Key: HIVE-439
>                 URL:
>             Project: Hadoop Hive
>          Issue Type: Improvement
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: Namit Jain
>         Attachments: hive.439.1.patch, hive.439.2.patch, hive.439.3.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:
> Bit, it also makes sense in HIVE to merge files whenever possible.

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