[
https://issues.apache.org/jira/browse/LUCENE-8450?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16574493#comment-16574493
]
Robert Muir commented on LUCENE-8450:
-------------------------------------
As mentioned on the mailing list, I don't think we should do this for
tokenfilters due to complexity: it is not just on the API side, but the
maintenance side too: worrying about how to keep all the tokenfilters correct.
I am sorry that some tokenfilters that really should be tokenizers extend the
wrong base class, but that problem should simply be fixed.
Separately I don't like the correctOffset() method that we already have on
tokenizer today. maybe it could be in the offsetattributeimpl or similar
instead. But at least today its just one method.
> 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".
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
