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https://issues.apache.org/jira/browse/MAPREDUCE-491?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Daehyun Kim updated MAPREDUCE-491:
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Status: Patch Available (was: In Progress)
> RAgzip: multiple map tasks for a large gzipped file
> ---------------------------------------------------
>
> Key: MAPREDUCE-491
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-491
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Affects Versions: 0.21.0
> Reporter: Daehyun Kim
> Assignee: Daehyun Kim
> Priority: Minor
> Fix For: 0.21.0
>
> Attachments: HADOOP-4652-v2.patch, HADOOP-4652-v3.patch,
> HADOOP-4652.path, MAPREDUCE-491.patch
>
>
> Currently, the hadoop processes gzipped files with only one map.
> We have made a patch that enables multiple map tasks for one large gzipped
> file. We call the patch RAgzip.
> To process multiple map tasks for gzipped file, you may use RAgzip by just
> changing InputFormat to RAGZIPInputFormat.
> The option used in RAGZIPInputFormat can be found at the javadoc of
> RAGZIPInputFormat part.
> RAgzip uses zlib's inflatePrime function which supports random access on a
> gzipped file.
> Since the inflatePrime is supported from the version of 1.2.2.4, it requires
> zlib 1.2.2.4 or higher. (We tested on zlib 1.2.3)
> RAgzip requires the preprocessing step that creates an access point (.ap)
> file, which is like the index of the gzipped file chunks.
> The access point(.ap) file is located in same path of the gzipped file.
> If there is a "/user/hadoop/test.gz", the .ap file is created with
> "/user/hadoop/test.gz.ap".
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