We need to improve in the hibernate. When we use the terms portability concers then this function work to handle currently work pretty well from Hibernate Query language(HQL). We can see the Quite lacking in the all other aspects.
When we use the SQL Data base that time we see in the SQL function can be referenced in many ways by user. When ever we use this type of aspect then we see the all database does not support the same set of function. In the Hibernate, Hibernate provide the logical function name for mapping to delegate which know how to render that particular function, perhaps even using a totally different physical function call.
In the other word we can say technically these type of function registration handled by the org.hibernate.dialect.function.SQLFunctionRegistry class which is intended to allow users to provice custom function definitions without having to provide a custom dialect.It is sort of implemented such that user can programatically register function with the org.hibernate.cfg.Configuration and those funcitons will be recognized for HQL. But we can say these type of specific behavior is not fully completed yet.