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https://issues.apache.org/jira/browse/LUCENE-2198?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12798388#action_12798388
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Simon Willnauer commented on LUCENE-2198:
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bq. So I think we should just provide ignore with CharArraySet, but if you feel
otherwise please comment.
While I read your proposal a possibly more flexible design came to my mind. We
could introduce a StemAttribute that has a method public boolean stem() used by
every stemmer to decide if a token should be stemmed. That way we decouple the
decision if a token should be stemmed from the stemming algorithm. This also
enables custom filters to set the values based on other reasons aside from a
term being in a set.
The default value for sure it true but can be set on any condition. inside an
analyzer we can add a filter right before the stemmer based on a CharArraySet.
Yet if the set is empty or null we simply leave the filter out.
> support protected words in Stemming TokenFilters
> ------------------------------------------------
>
> Key: LUCENE-2198
> URL: https://issues.apache.org/jira/browse/LUCENE-2198
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Analysis
> Affects Versions: 3.0
> Reporter: Robert Muir
> Priority: Minor
>
> This is from LUCENE-1515
> I propose that all stemming TokenFilters have an 'exclusion set' that
> bypasses any stemming for words in this set.
> Some stemming tokenfilters have this, some do not.
> This would be one way for Karl to implement his new swedish stemmer (as a
> text file of ignore words).
> Additionally, it would remove duplication between lucene and solr, as they
> reimplement snowballfilter since it does not have this functionality.
> Finally, I think this is a pretty common use case, where people want to
> ignore things like proper nouns in the stemming.
> As an alternative design I considered a case where we generalized this to
> CharArrayMap (and ignoring words would mean mapping them to themselves),
> which would also provide a mechanism to override the stemming algorithm. But
> I think this is too expert, could be its own filter, and the only example of
> this i can find is in the Dutch stemmer.
> So I think we should just provide ignore with CharArraySet, but if you feel
> otherwise please comment.
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