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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-4509) Make CompressingStoredFieldsFormat the new default StoredFieldsFormat impl
Date Fri, 26 Oct 2012 20:31:12 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-4509?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13485182#comment-13485182
] 

Robert Muir commented on LUCENE-4509:
-------------------------------------

I'd say to make progress for the default we want to look at:
* make a concrete impl of CompressingStoredFieldsFormat called Lucene41, hardwired to the
defaults and add file format docs?
  This way, we don't have to support all of the Compression options/layouts in the default
codec (if someone wants that, 
  encourage them to make their own codec with the Compressed settings they like). Back compat
is much 
  less costly as the parameters are fixed. File format docs are easier :)
* should we s/uncompression/decompression/ across the board?
* tests already look pretty good. I can try to work on some additional ones to try to break
it like we did with BlockPF.
* there is some scary stuff (literal decompressions etc) uncovered by the clover report: https://builds.apache.org/job/Lucene-Solr-Clover-4.x/49/clover-report/org/apache/lucene/codecs/compressing/CompressionMode.html
We should make sure any special cases are tested.

                
> Make CompressingStoredFieldsFormat the new default StoredFieldsFormat impl
> --------------------------------------------------------------------------
>
>                 Key: LUCENE-4509
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4509
>             Project: Lucene - Core
>          Issue Type: Wish
>          Components: core/store
>            Reporter: Adrien Grand
>            Priority: Minor
>
> What would you think of making CompressingStoredFieldsFormat the new default StoredFieldsFormat?
> Stored fields compression has many benefitsĀ :
>  - it makes the I/O cache work for us,
>  - file-based index replication/backup becomes cheaper.
> Things to know:
>  - even with incompressible data, there is less than 0.5% overhead with LZ4,
>  - LZ4 compression requires ~ 16kB of memory and LZ4 HC compression requires ~ 256kB,
>  - LZ4 uncompression has almost no memory overhead,
>  - on my low-end laptop, the LZ4 impl in Lucene uncompresses at ~ 300mB/s.
> I think we could use the same default parameters as in CompressingCodec :
>  - LZ4 compression,
>  - in-memory stored fields index that is very memory-efficient (less than 12 bytes per
block of compressed docs) and uses binary search to locate documents in the fields data file,
>  - 16 kB blocks (small enough so that there is no major slow down when the whole index
would fit into the I/O cache anyway, and large enough to provide interesting compression ratiosĀ ;
for example Robert got a 0.35 compression ratio with the geonames.org database).
> Any concerns?

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