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https://issues.apache.org/jira/browse/HIVE-439?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12717820#action_12717820
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Namit Jain commented on HIVE-439:
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Instead of having a map-only job to do the concatenation, I think we should use
a map-reduce job.
This way, when sorting properties of a table are maintained in the metastore,
they can be preserved.
> merge small files whenever possible
> -----------------------------------
>
> Key: HIVE-439
> URL: https://issues.apache.org/jira/browse/HIVE-439
> Project: Hadoop Hive
> Issue Type: Improvement
> Components: Query Processor
> Reporter: Namit Jain
> Assignee: Namit Jain
>
> 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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