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From "Clinton Gormley (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (LUCENE-4766) Pattern token filter which emits a token for every capturing group
Date Sun, 10 Feb 2013 12:37:12 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-4766?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Clinton Gormley updated LUCENE-4766:
------------------------------------

    Attachment: LUCENE-4766.patch

Patch implementing org.apache.lucene.analysis.pattern.PatternCaptureGroupTokenFilter and org.apache.lucene.analysis.pattern.TestPatternCaptureGroupTokenFilter
                
> Pattern token filter which emits a token for every capturing group
> ------------------------------------------------------------------
>
>                 Key: LUCENE-4766
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4766
>             Project: Lucene - Core
>          Issue Type: New Feature
>          Components: modules/analysis
>    Affects Versions: 4.1
>            Reporter: Clinton Gormley
>            Priority: Minor
>              Labels: analysis, feature, lucene
>             Fix For: 4.2
>
>         Attachments: LUCENE-4766.patch
>
>
> The PatternTokenizer either functions by splitting on matches, or allows you to specify
a single capture group.  This is insufficient for my needs. Quite often I want to capture
multiple overlapping tokens in the same position.
> I've written a pattern token filter which accepts multiple patterns and emits tokens
for every capturing group that is matched in any pattern.
> Patterns are not anchored to the beginning and end of the string, so each pattern can
produce multiple matches.
> For instance a pattern like "(([a-z]+)(\d*))" when matched against "abc123def456" would
produce the tokens:
>     abc123, abc, 123, def456, def, 456
> Multiple patterns can be applied, eg these patterns could be used for camelCase analysis:
>     "([A-Z]{2,})",
>     "(?<![A-Z])([A-Z][a-z]+)",
>     "(?:^|\\b|(?<=[0-9_])|(?<=[A-Z]{2}))([a-z]+)",
>     "([0-9]+)"
> When matched against the string "letsPartyLIKEits1999_dude", they would produce the tokens:
>     lets, Party, LIKE, its, 1999, dude
> If no token is emitted, the original token is preserved. 
> If the preserveOriginal flag is true, it will output the full original token (ie "letsPartyLIKEits1999_dude")
in addition to any matching tokens (but in this case, if a matching token is identical to
the original, it will only emit one copy of the full token).
> Multiple patterns are required to allow overlapping captures, but also means that patterns
are less dense and easier to understand.
> This is my first Java code, so apologies if I'm doing something stupid.

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