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https://issues.apache.org/jira/browse/HIVE-439?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Zheng Shao updated HIVE-439:
----------------------------
Resolution: Fixed
Release Note: HIVE-439. Merge small files after a map-only job. (Namit Jain
via zshao)
Hadoop Flags: [Reviewed]
Status: Resolved (was: Patch Available)
Committed. There is a small change: the default value for
hive.merge.size.per.mapper is changed to 1000000000 (1GB) from 10GB.
Thanks Namit!
> 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, hive.439.5.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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