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From "Yonik Seeley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1799) Unicode compression
Date Wed, 28 Jul 2010 18:58:21 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1799?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12893306#action_12893306
] 

Yonik Seeley commented on LUCENE-1799:
--------------------------------------

bq. in general you wont get much compression for chinese.. id say max 25%

Ah, OK.
I just tried russian w/ whitespace analyzer used to split and did get a good size savings:

UTF8_size=11056  BOCU-1_size=6810  BOCU-1_slowdown=32%

> Unicode compression
> -------------------
>
>                 Key: LUCENE-1799
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1799
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: Store
>    Affects Versions: 2.4.1
>            Reporter: DM Smith
>            Priority: Minor
>         Attachments: Benchmark.java, LUCENE-1779.patch, LUCENE-1799.patch, LUCENE-1799.patch,
LUCENE-1799.patch, LUCENE-1799.patch, LUCENE-1799.patch, LUCENE-1799.patch, LUCENE-1799.patch,
LUCENE-1799.patch, LUCENE-1799.patch, LUCENE-1799.patch, LUCENE-1799.patch, LUCENE-1799.patch,
LUCENE-1799.patch, LUCENE-1799.patch, LUCENE-1799_big.patch
>
>
> In lucene-1793, there is the off-topic suggestion to provide compression of Unicode data.
The motivation was a custom encoding in a Russian analyzer. The original supposition was that
it provided a more compact index.
> This led to the comment that a different or compressed encoding would be a generally
useful feature. 
> BOCU-1 was suggested as a possibility. This is a patented algorithm by IBM with an implementation
in ICU. If Lucene provide it's own implementation a freely avIlable, royalty-free license
would need to be obtained.
> SCSU is another Unicode compression algorithm that could be used. 
> An advantage of these methods is that they work on the whole of Unicode. If that is not
needed an encoding such as iso8859-1 (or whatever covers the input) could be used.    

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