Variant functions

By default, user-defined functions are variant. Variant functions can return different values or have varying side effects, given the same arguments.

For example, a function that returns the current date or time is a variant function. However, a function that appears nonvariant can also have varying side effects, such as updating a table or external file.

The cost of defining a nonvariant function as variant is low: you might experience slightly diminished performance. However, the cost of defining a function that exhibits variant behavior as nonvariant can be high, because a query might return incorrect results.

Most functions are not variant; marking them as nonvariant improves performance. If the function is nonvariant, the database server might cache the return values of expensive functions or run parallel queries. Functional indexes are only allowed on nonvariant functions.

See the HCL OneDB™ User-Defined Routines and Data Types Developer's Guide for more information.