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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-54) SequenceFile should compress blocks, not individual entries
Date Thu, 24 Aug 2006 06:48:35 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-54?page=comments#action_12430091 ] 
            
Owen O'Malley commented on HADOOP-54:
-------------------------------------

A minor quible is that when you are basically implementing an Enum, we should probably use
the name "valueOf(String)" instead of "getCompressionType(String)" to be forward compatible
with the java 1.5 signature for that functionality.

I'd also like to see some performance numbers for straight reads and writes of the seq3 and
seq4 block compressed files.

> SequenceFile should compress blocks, not individual entries
> -----------------------------------------------------------
>
>                 Key: HADOOP-54
>                 URL: http://issues.apache.org/jira/browse/HADOOP-54
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: io
>    Affects Versions: 0.2.0
>            Reporter: Doug Cutting
>         Assigned To: Arun C Murthy
>             Fix For: 0.6.0
>
>         Attachments: SequenceFile.20060821.patch, SequenceFile.20060821.perfomance.txt,
SequenceFile.20060822.tgz, SequenceFile.updated.final.patch, SequenceFiles.final.patch, SequenceFiles.patch,
SequenceFilesII.patch, VIntCompressionResults.txt
>
>
> SequenceFile will optionally compress individual values.  But both compression and performance
would be much better if sequences of keys and values are compressed together.  Sync marks
should only be placed between blocks.  This will require some changes to MapFile too, so that
all file positions stored there are the positions of blocks, not entries within blocks.  Probably
this can be accomplished by adding a getBlockStartPosition() method to SequenceFile.Writer.

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