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From "Namit Jain (JIRA)" <>
Subject [jira] Commented: (HIVE-629) concat files needed for map-reduce jobs also
Date Wed, 15 Jul 2009 17:50:14 GMT


Namit Jain commented on HIVE-629:

1. The number of reducers are determined from "hive.merge.size.per.task"
2. We use random()
3. I am not sure about that - by default, it should be disabled in case of a map-reduce job.
Only in very specific cases, it is being turned on, where the user knows exactly what is he
doing and can set the size appropriately.

> concat files needed for map-reduce jobs also
> --------------------------------------------
>                 Key: HIVE-629
>                 URL:
>             Project: Hadoop Hive
>          Issue Type: Improvement
>          Components: Query Processor
>    Affects Versions: 0.4.0
>            Reporter: Namit Jain
>            Assignee: Namit Jain
>         Attachments: hive.629.1.patch
> Currently, hive concatenates files only if the job under consideration is a map-only
> I got some requests from some users, where they want this behavior for map-reduce jobs
also - it may not be a good idea to turn it on by default.
> But, we should provide an option to the user where the concatenation can happen even
for map-reduce jobs.

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