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From "Robert Muir (JIRA)" <>
Subject [jira] [Commented] (LUCENE-4509) Make CompressingStoredFieldsFormat the new default StoredFieldsFormat impl
Date Fri, 26 Oct 2012 21:33:12 GMT


Robert Muir commented on LUCENE-4509:

No, I'm referring to the second packed ints structure (start offset within a block)
> Make CompressingStoredFieldsFormat the new default StoredFieldsFormat impl
> --------------------------------------------------------------------------
>                 Key: LUCENE-4509
>                 URL:
>             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 database).
> Any concerns?

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