[jira] Reopened: (LUCENE-400) NGramFilter -- construct n-grams from a TokenStream

["Grant Ingersoll (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/LUCENE-400?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Grant Ingersoll reopened LUCENE-400:
------------------------------------


Good catch, Steve.  I will reopen, as a word based ngram filter is useful.

> NGramFilter -- construct n-grams from a TokenStream
> ---------------------------------------------------
>
>                 Key: LUCENE-400
>                 URL: https://issues.apache.org/jira/browse/LUCENE-400
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Analysis
>    Affects Versions: unspecified
>         Environment: Operating System: All
> Platform: All
>            Reporter: Sebastian Kirsch
>            Priority: Minor
>         Attachments: NGramAnalyzerWrapper.java, NGramAnalyzerWrapperTest.java, NGramFilter.java, NGramFilterTest.java
>
>
> This filter constructs n-grams (token combinations up to a fixed size, sometimes
> called "shingles") from a token stream.
> The filter sets start offsets, end offsets and position increments, so
> highlighting and phrase queries should work.
> Position increments > 1 in the input stream are replaced by filler tokens
> (tokens with termText "_" and endOffset - startOffset = 0) in the output
> n-grams. (Position increments > 1 in the input stream are usually caused by
> removing some tokens, eg. stopwords, from a stream.)
> The filter uses CircularFifoBuffer and UnboundedFifoBuffer from Apache
> Commons-Collections.
> Filter, test case and an analyzer are attached.

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