Re: Returning null from Userdefined C function

Andrew Selle <aselle@upl.cs.wisc.edu> writes:
> Obviously, there must be some way to create a NULL text * return 
> variable,

You would think that, but you'd be wrong :-( --- at least for current
releases; this problem has been fixed for 7.1 by creating a new API
for user-defined functions.

With the old API, for the case of single-argument functions, you can
fake it via an ugly kluge: declare a second argument "bool *isNull"
(at the C level only, not in the SQL definition) and set *isNull to
TRUE if you want to return a NULL.  This does not work if the function
doesn't have exactly one SQL argument, however.
        regards, tom lane