[jira] Updated: (LUCENE-1799) Unicode compression

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[jira] Updated: (LUCENE-1799) Unicode compression

JIRA jira@apache.org

     [ https://issues.apache.org/jira/browse/LUCENE-1799?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Uwe Schindler updated LUCENE-1799:
----------------------------------

    Attachment: LUCENE-1799.patch

Here is a 100% legally valid implementation:

- Linking to icu4j-charsets is done dynamically by reflection. If you don't have ICU4J charsets in your classpath, the attribute throws explaining exception
- We dont need to ship the rather large JAR file with Lucene just for this class
- We dont have legal patent problems as we neither ship the API nor use it directly
- The backside is that the Test simple prints a warning but passes, so the class is not tested until you install icu4j-charsets.jar. We can put the JAR file on hudson, so it can be used during nightly builds. Or we download it dynamically on build.

I added further improvements to the encoder ittself:
- less variables
- correct error handling for encoding errors
- remove floating point from main loop

> 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: LUCENE-1799.patch, LUCENE-1799.patch, LUCENE-1799.patch, LUCENE-1799.patch, LUCENE-1799.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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