You can call user-defined functions directly in the CONTAINS
clause as long as the function satisfies the requirements for being named in a SQL statement. The caller must also have EXECUTE
privilege on the function.
For example, assuming the function french returns the French equivalent of an English word, you can search on the French word for cat by writing:
SELECT SCORE(1), title from news WHERE CONTAINS(text, french('cat'), 1) > 0 ORDER BY SCORE(1);
Oracle Database SQL Language Reference for more information about creating user functions and calling user functions from SQL