Re: Minor point about contrib/xml2 functions "IMMUTABLE" marking

Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > Neil Conway wrote:
> >> If a function's return value for a particular set of arguments could
> >> change within a single table scan, the function is volatile -- ISTM
> >> xslt_process() clearly falls within that definition.
>
> > My thought was that a web page lookup is going to be a very expensive
> > operation, so you would not want it to requery inside a transaction.
>
> > It is not like random() where you want it to be re-called and it is
> > inexpensive.
>
> "It's too expensive" is not a valid rationale for claiming that
> something is stable when it is not. In any case, you have fallen into
> the all too common trap of supposing that these labels have something
> to do with caching function results. Calling it stable is not going
> to improve performance, only create a risk of wrong answers.

Well, should be marked as VOLATILE? A web lookup?

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073