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https://issues.apache.org/jira/browse/LUCENE-5057?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Adrien Grand resolved LUCENE-5057.
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Resolution: Won't Fix
I checked with Luca and this is a dictionary issue, fietsen and fiets are both
considered as stems of fietsen with the dutch dictionary.
For people who have stemming issues, this is very easy to check whether the
issue is in Lucene or in the dictionary by installing hunspell-tools (apt-get
install hunspell-tools on Debian and related distributions) and running:
{noformat}
% echo fietsen > tmp
% /usr/lib/hunspell/analyze nl_NL.aff nl_NL.dic tmp
> fietsen
analyze(fietsen) = st:fietsen
analyze(fietsen) = st:fiets fl:N
stem(fietsen) = fietsen
stem(fietsen) = fiets
{noformat}
In this particular case, we can see that fietsen is both a stem (1st line) and
a variation of fiets with the affix identified with "N".
> Hunspell stemmer generates multiple tokens
> ------------------------------------------
>
> Key: LUCENE-5057
> URL: https://issues.apache.org/jira/browse/LUCENE-5057
> Project: Lucene - Core
> Issue Type: Improvement
> Affects Versions: 4.3
> Reporter: Luca Cavanna
> Assignee: Adrien Grand
>
> The hunspell stemmer seems to be generating multiple tokens: the original
> token plus the available stems.
> It might be a good thing in some cases but it seems to be a different
> behaviour compared to the other stemmers and causes problems as well. I would
> rather have an option to decide whether it should output only the available
> stems, or the stems plus the original token. I'm not sure though if it's
> possible to have only a single stem indexed, which would be even better in my
> opinion. When I look at how snowball works only one token is indexed, the
> stem, and that works great. Probably there's something I'm missing in how
> hunspell works.
> Here is my issue: I have a query composed of multiple terms, which is
> analyzed using stemming and a boolean query is generated out of it. All fine
> when adding all clauses as should (OR operator), but if I add all clauses as
> must (AND operator), then I can get back only the documents that contain the
> stem originated by the exactly same original word.
> Example for the dutch language I'm working with: fiets (means bicycle in
> dutch), its plural is fietsen.
> If I index "fietsen" I get both "fietsen" and "fiets" indexed, but if I index
> "fiets" I get the only "fiets" indexed.
> When I query for "fietsen whatever" I get the following boolean query:
> field:fiets field:fietsen field:whatever.
> If I apply the AND operator and use must clauses for each subquery, then I
> can only find the documents that originally contained "fietsen", not the ones
> that originally contained "fiets", which is not really what stemming is about.
> Any thoughts on this? I also wonder if it can be a dictionary issue since I
> see that different words that have the word "fiets" as root don't get the
> same stems, and using the AND operator at query time is a big issue.
> I would love to contribute on this and looking forward to your feedback.
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