Tatsuo Ishii <ishii@postgresql.org> writes:
> What is your locale?
>> It was en_EN.UTF-8. Interesting. With C it fails...
> Yes, pg_trgm seems to have problems with multibyte + C locale.
It's not a problem, it's just pilot error, or possibly inadequate
documentation. pg_trgm uses the locale's definition of "alpha",
"digit", etc. In C locale only basic ASCII letters and digits will be
recognized as word constituents.
regards, tom lane