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From "Arun C Murthy (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-54) SequenceFile should compress blocks, not individual entries
Date Thu, 20 Jul 2006 18:52:15 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-54?page=comments#action_12422470 ] 
            
Arun C Murthy commented on HADOOP-54:
-------------------------------------

Sounds good... looks like we're all on the same page; I'll get going on this.

Appreciate both of you spending time... I'll also keep in mind Doug's thoughts on documenting
the file-format for SequenceFile.

thanks!
Arun

> 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: 0.5.0
>
>         Attachments: 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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