I think many of us think certain things happen in Zebra when they actually happen in Koha before the query ever reaches Zebra ;).
As for stemming, theoretically the language obtained via “C4::Templates::getlanguage($cgi, 'intranet');” should filter down into the Snowball stemming. If it isn’t working in French, it might be because the right locale isn’t being passed to Snowball correctly. That’s very possible as I think we’re using arbitrary language codes rather than standard locales in some cases. It looks like there is a fallback to English in C4::Templates::getlanguage() as well. If it’s not working for French, it probably just needs a tweak!
Yeah, I first heard about Snowball when reading through Zebra docs, and I was pleasantly surprised when I saw that Lingua::Stem::Snowball existed as a Perl interface for the C program.
David Cook
Systems Librarian
Prosentient Systems
72/330 Wattle St, Ultimo, NSW 2007
From: koha-devel-bounces@lists.koha-community.org [mailto:koha-devel-bounces@lists.koha-community.org] On Behalf Of Mathieu Saby
Sent: Wednesday, 27 August 2014 7:30 PM
To: koha-devel@lists.koha-community.org
Subject: Re: [Koha-devel] Stemming and zebra
Hi
I had always thought stemming was made by Zebra, and only in english!
In fact the algorithm for french language is here:
http://snowball.tartarus.org/algorithms/french/stemmer.html
(Lingua::Stem::Snowball is a Perl interface to the C version of the Snowball stemmers)
Mathieu Saby
Le 27/08/2014 10:22, David Cook a écrit :
Hi Francois:
I wrote an email earlier on my tablet, but not 100% sure if it got sent. In any case, I’m writing again now!
You’ll want to look at C4::Search::_build_stemmed_operand().
Zebra doesn’t actually do any stemming itself. If you read through the Zebra docs (if you’re masochistic), you’ll notice that they say explicitly that Zebra doesn’t do any stemming, but that you can do stemming (using a stemmer like Snowball) while building a query. That’s exactly what we do in Koha.
The Perl module that does the stemming is Lingua::Stem::Snowball.
However, you might notice that your query’s operands aren’t always stemmed properly. I haven’t looked in a while, but I think it’s because we don’t build our queries very well at all (when not using QueryParser).
If you want to understand why you’re getting “skills” and “fishxsdfe” in your results, I would suggest running some tests ( using “Data::Dumper” and “warn” ) so that you can see your query as it is built.
I have a lot of work I want to do on C4::Search::buildQuery, but just don’t have the time :/.
Unfortunately, at the moment, there is no stemming when using the QueryParser. However, fortunately, using Lingua::Stem::Snowball with QueryParser would be really really easy. I think that I’ve written a note on how to do that somewhere on Bugzilla or maybe on Trello…
I hope that helps! Feel free to send me an email or shout at me on IRC if you want any clarification. I know I probably didn’t make it any clearer but hopefully this might help you on your path to understanding.
David Cook
Systems Librarian
Prosentient Systems
72/330 Wattle St, Ultimo, NSW 2007
From: koha-devel-bounces@lists.koha-community.org [mailto:koha-devel-bounces@lists.koha-community.org] On Behalf Of Francois Charbonnier
Sent: Wednesday, 27 August 2014 2:09 AM
To: koha-devel@lists.koha-community.org
Subject: [Koha-devel] Stemming and zebra
Hello,
I have tested the QueryStemming system preference on Koha 3.14 (my local installation) and I'm wondering, does zebra just right truncate the words or is there an algorithm to find the stems?
I use ICU and I have enabled "QueryWeightFields". I don't have automatic truncation or fuzzy search on. I use these words for my tests: ski, skiing, skills
 fish, fished, fishing, fisher, fishxsdfe
Each time, with QueryStemming on, skills and fishxsdfe come out in the search results. Is it what I should expect? "Skills", maybe but "fishxsdfe"?
Do you know how it works? or have a good example that would help me to understand?
Thanks!
--
François Charbonnier,
Bibl. prof. / Chef de produitsTél. : (888) 604-2627
francois.charbonnier@inLibro.cominLibro | pour esprit libre | www.inLibro.com
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