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From "Arun C Murthy (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-54) SequenceFile should compress blocks, not individual entries
Date Tue, 08 Aug 2006 07:52:15 GMT
     [ http://issues.apache.org/jira/browse/HADOOP-54?page=all ]

Arun C Murthy updated HADOOP-54:
--------------------------------

    Attachment: SequenceFiles.patch

Here's the patch for block compressed SequenceFiles.

Main attractions:
a) Three different writers for SequenceFiles: Writer, RecordCompressWriter, BlockCompressWriter
(with a factory to create the different writers).
b) The 'raw' apis are significantly different (as per previous discussions here)
c) Fixed SequenceFile.Sorter to take advantage of new 'raw' apis and some minor tweak/enhancements
there.

As per Owen's suggestion, I've only uploaded the patch... once I get some feedback, I'll go
ahead and change the 'status' to 'Patch Available'.

> 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: SequenceFiles.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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