Version resolution

Normally, the currently active version of an SQL function is used for invocation of the function.

However, if the invocation is a recursive invocation that occurs inside the body of the same function, and the currently active version has changed since the original invocation, the active version is not used. The version that is used in the original invocation is used for any recursive invocation until the entire function completes. This preserves the semantics of the version that is used by the original invocation.

The version used in the original invocation is also used when the recursive invocation is indirect. For example, assume that function FN1 invokes function FN2, which in turn invokes FN1 (indirect, recursive invocation). The invocation of function FN1 in function FN2 uses the version of FN1 that is active at the time of the original invocation of function FN1.

Since the currently active version is used at the next invocation (except in recursive invocations), it is possible that two or more versions of the same function can be run by a given thread. For example, an invocation of function FN1 in an application causes the currently active version of FN1 to load and execute. During or after execution of the original invocation of FN1, an ALTER FUNCTION statement that specifics ACTIVE VERSION FN1_V2 is run and changes the active version of the function FN1 to version FN1_V2. Subsequent invocations of function FN1 from the same thread will load and execute the currently active version of the function, FN1_V2.