[ 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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