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https://issues.apache.org/jira/browse/LUCENE-8450?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16576805#comment-16576805
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Robert Muir commented on LUCENE-8450:
-------------------------------------
{quotdine}
I'm also reluctant to place WDF early in the chain because it does some weird
recombinations that I only want to happen after I have already had a chance to
do more tightly-scoped processing like handling numbers: decimals, fractions
and the like.
{quote}
I get that sentiment, but i would like for us to think a little bit farther
than just "before" for "after" according to the current status quo. The fact of
life here is, it seems you want to customize the tokenizer in certain ways
(e.g. numerics) but also other ways such as hyphens or similar. I don't think
its abnormal or a strange use-case, I think we just don't support it well with
the current APIs.
> 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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