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https://issues.apache.org/jira/browse/LUCENE-1488?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Robert Muir updated LUCENE-1488:
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Attachment: ICUAnalyzer.patch
i've attached a patch for 'ICUAnalyzer'. I see that some things involving Token
have changed but I created it before that point.
I stole the unit tests from standard analyzer and put comments as to why
certain ones arent appropriate and disabled those.
i added some unit tests that demonstrate some of the value, correct analysis
for arabic numerals, hindi text, decomposed latin diacritics, hebrew
punctuation, cantonese and linear-b text outside of the BMP, etc.
one issue is that setMaxTokenLength() doesnt work correctly for values > 255
because CharTokenizer has a hardcoded private limit of 255 that i can't
override. This is a problem since i use WhitespaceTokenizer first and then
break down those tokens with the RBBI.
> issues with standardanalyzer on multilingual text
> -------------------------------------------------
>
> Key: LUCENE-1488
> URL: https://issues.apache.org/jira/browse/LUCENE-1488
> Project: Lucene - Java
> Issue Type: Wish
> Components: contrib/analyzers
> Reporter: Robert Muir
> Priority: Minor
> Attachments: ICUAnalyzer.patch
>
>
> The standard analyzer in lucene is not exactly unicode-friendly with regards
> to breaking text into words, especially with respect to non-alphabetic
> scripts. This is because it is unaware of unicode bounds properties.
> I actually couldn't figure out how the Thai analyzer could possibly be
> working until i looked at the jflex rules and saw that codepoint range for
> most of the Thai block was added to the alphanum specification. defining the
> exact codepoint ranges like this for every language could help with the
> problem but you'd basically be reimplementing the bounds properties already
> stated in the unicode standard.
> in general it looks like this kind of behavior is bad in lucene for even
> latin, for instance, the analyzer will break words around accent marks in
> decomposed form. While most latin letter + accent combinations have composed
> forms in unicode, some do not. (this is also an issue for asciifoldingfilter
> i suppose).
> I've got a partially tested standardanalyzer that uses icu Rule-based
> BreakIterator instead of jflex. Using this method you can define word
> boundaries according to the unicode bounds properties. After getting it into
> some good shape i'd be happy to contribute it for contrib but I wonder if
> theres a better solution so that out of box lucene will be more friendly to
> non-ASCII text. Unfortunately it seems jflex does not support use of these
> properties such as [\p{Word_Break = Extend}] so this is probably the major
> barrier.
> Thanks,
> Robert
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