Re: [tsvector] to_tsvector called multiple times - Mailing list pgsql-general

From Oleg Bartunov
Subject Re: [tsvector] to_tsvector called multiple times
Date
Msg-id CAF4Au4zaXvdLPaqOtoawB=bnGPO=3jdZO5EDLm4jAc8cCFvJtQ@mail.gmail.com
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In response to [tsvector] to_tsvector called multiple times  ("Sven R. Kunze" <srkunze@tbz-pariv.de>)
Responses Re: [tsvector] to_tsvector called multiple times
List pgsql-general
You can ask http://snowball.tartarus.org/ for stemmer. Meanwhile,
you can have small personal dictionary (before stemmer) with such exceptions, for example, use synonym template

system system

Oleg


On Tue, May 26, 2015 at 11:18 AM, Sven R. Kunze <srkunze@tbz-pariv.de> wrote:
Hi everybody,

the following stemming results made me curious:

select to_tsvector('german', 'systeme'); > 'system':1
select to_tsvector('german', 'systemes'); > 'system':1
select to_tsvector('german', 'systems'); > 'system':1
select to_tsvector('german', 'systemen'); > 'system':1
select to_tsvector('german', 'system'); >  'syst':1


First of all, this seems to be a bug in the German stemmer. Where can I fix it?

Second, and more importantly, as I understand it, the stemmed version of a word should be considered normalized. That is, all other versions of that stem should be mapped to it as well. The interesting problem here is that PostgreSQL maps the stem itself ('system') to a completely different stem ('syst').

Should a stem not remain stable even when to_tsvector is called on it multiple times?

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Sven R. Kunze
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