Re: function side effects

"Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
> Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Those classifications are meant as planner directives; they are
>> NOT meant to be bulletproof.  Hanging database integrity
>> guarantees on whether a "non volatile" function changes anything
>> is entirely unsafe.  To give just one illustration of the
>> problems, a nonvolatile function is allowed to call a volatile
>> one.
> Could it work to store a flag in each process to indicate when it is
> executing a non-volatile function, and throw an error on any attempt
> to call a volatile function or modify the database?

It's *not an error* for a nonvolatile function to call a volatile one.
At least it's never been in the past, and I'm sure you'd break some
applications if you made it so in the future.
        regards, tom lane