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From "Adrien Grand (JIRA)" <j...@apache.org>
Subject [jira] [Created] (LUCENE-4509) Make CompressingStoredFieldsFormat the new default StoredFieldsFormat impl
Date Fri, 26 Oct 2012 18:05:12 GMT
Adrien Grand created LUCENE-4509:
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             Summary: 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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