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http://issues.apache.org/jira/browse/HADOOP-54?page=comments#action_12420563 ] 

Doug Cutting commented on HADOOP-54:
------------------------------------

I like this proposal.  Long-term, custom compressors make good sense, but for 
the first version let's just use a fixed algorithm and add that as a separate 
pass, ok?  That could be a separate issue in Jira.

> SequenceFile should compress blocks, not individual entries
> -----------------------------------------------------------
>
>          Key: HADOOP-54
>          URL: http://issues.apache.org/jira/browse/HADOOP-54
>      Project: Hadoop
>         Type: Improvement

>   Components: io
>     Versions: 0.2.0
>     Reporter: Doug Cutting
>     Assignee: Michel Tourn
>      Fix For: 0.5.0

>
> 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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