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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, 22 Aug 2006 11:31:22 GMT
     [ http://issues.apache.org/jira/browse/HADOOP-54?page=all ]

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

    Attachment: SequenceFile.20060822.tgz

Here's a patch with a minor tweak to the Sorter (to reuse ValueBytes objects across spills).

I've also attached results of another set of benchmark runs (w/o -check and with -fast) -
I've also run it against instrumented code to show no. of ValueBytes objects and total bytes
allocated for raw values (note: doesn't imply all of them are allocated at the same time;
just total of bytes allocated in the CompressedBytes.reset/UncompressedBytes.reset calls over
lifetime of each test case).

> 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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