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https://issues.apache.org/jira/browse/LUCENE-2909?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12991316#comment-12991316
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Robert Muir commented on LUCENE-2909:
-------------------------------------

Is the bug really in NGramTokenFilter? 

This seems to be a larger problem that would affect all tokenfilters that break 
larger tokens
into smaller ones and recalculate offsets, right?

For example: EdgeNGramTokenFilter, ThaiWordFilter, SmartChineseAnalyzer's 
WordTokenFilter, etc?

I think WordDelimiterFilter has special code that might avoid the problem (line 
352), so it might
be ok.

Is there any better way we could solve this: for example maybe instead of the 
tokenizer calling
correctOffset() it gets called somewhere else? This seems to be what is causing 
the problem.


> NGramTokenFilter may generate offsets that exceed the length of original text
> -----------------------------------------------------------------------------
>
>                 Key: LUCENE-2909
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2909
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: contrib/analyzers
>    Affects Versions: 2.9.4
>            Reporter: Shinya Kasatani
>            Assignee: Koji Sekiguchi
>            Priority: Minor
>         Attachments: TokenFilterOffset.patch
>
>
> Whan using NGramTokenFilter combined with CharFilters that lengthen the 
> original text (such as "ß" -> "ss"), the generated offsets exceed the length 
> of the origianal text.
> This causes InvalidTokenOffsetsException when you try to highlight the text 
> in Solr.
> While it is not possible to know the accurate offset of each character once 
> you tokenize the whole text with tokenizers like KeywordTokenizer, 
> NGramTokenFilter should at least avoid generating invalid offsets.

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