The problem: while partial matches can normally be done or stemming works when text is in the English language, in other languages like Chinese, only an exact match works.

The problem is a misconfiguration of the index: other languages besides English are supported. Setting LANGUAGE_FIELD to the desired language enables the stemmer for that specific language.

The supported languages are Arabic, Basque, Catalan, Danish, Dutch, English, Finnish, French, German, Greek, Hungarian, Indonesian, Irish, Italian, Lithuanian, Nepali, Norwegian, Portuguese, Romanian, Russian, Spanish, Swedish, Tamil, Turkish, and Chinese

References

Refer to the documentation for the Chinese language support and to the description of the option LANGUAGE_FIELD from FT.CREATE documentation.