[tsvector] to_tsvector called multiple times

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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