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https://issues.apache.org/jira/browse/LUCENE-8450?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16574825#comment-16574825
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Robert Muir commented on LUCENE-8450:
-------------------------------------
I feel pretty strongly that we shouldn't go this route. The thing dividing text
up into tokens, tokenizer is the lucene class for that.
Also when i say maintenance side just look at the offensive filters that really
should be tokenizers: they are all a real nightmare: cjkbigramfilter,
worddelimiterfilter, etc. These things are monstrously complex and difficult to
work with: its clearly not what a tokenfilter should be doing.
I don't want to change this situation into "differently broken" where somehow
now we have to add logic to *hundreds* of tokenfilters when we could just fix
the *2 or 3* bad ones such as wdf to be tokenizers instead.
> Enable TokenFilters to assign offsets when splitting tokens
> -----------------------------------------------------------
>
> Key: LUCENE-8450
> URL: https://issues.apache.org/jira/browse/LUCENE-8450
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Mike Sokolov
> Priority: Major
> Attachments: offsets.patch
>
>
> CharFilters and TokenFilters may alter token lengths, meaning that subsequent
> filters cannot perform simple arithmetic to calculate the original
> ("correct") offset of a character in the interior of the token. A similar
> situation exists for Tokenizers, but these can call
> CharFilter.correctOffset() to map offsets back to their original location in
> the input stream. There is no such API for TokenFilters.
> This issue calls for adding an API to support use cases like highlighting the
> correct portion of a compound token. For example the german word
> "außerstand" (meaning afaict "unable to do something") will be decompounded
> and match "stand and "ausser", but as things are today, offsets are always
> set using the start and end of the tokens produced by Tokenizer, meaning that
> highlighters will match the entire compound.
> I'm proposing to add this method to `TokenStream`:
> {{ public CharOffsetMap getCharOffsetMap();}}
> referencing a CharOffsetMap with these methods:
> {{ int correctOffset(int currentOff);}}
> {{ int uncorrectOffset(int originalOff);}}
>
> The uncorrectOffset method is a pseudo-inverse of correctOffset, mapping from
> original offset forward to the current "offset space".
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