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From "Adrien Grand (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-4509) Make CompressingStoredFieldsFormat the new default StoredFieldsFormat impl
Date Fri, 26 Oct 2012 21:17:12 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-4509?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13485205#comment-13485205
] 

Adrien Grand commented on LUCENE-4509:
--------------------------------------

bq. should we s/uncompression/decompression/ across the board?

If decompression sounds better, let's do this!

bq. here is some scary stuff (literal decompressions etc) uncovered by the clover report.
We should make sure any special cases are tested.

I can work on it next week.
                
> 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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