Re: non-cachable 'C' language functions

Forest Wilkinson <fspam(at)home(dot)com> writes:
> Is my understanding correct? What should I do about it? The postgresql
> 6.5.2 docs for CREATE FUNCTION don't tell me how to make my functions
> non-cachable.

6.5 doesn't pay any attention to proiscachable, AFAIR. 7.0 does, but
it defaults to assuming proiscachable = FALSE; you have to say
"with (iscachable)" in CREATE FUNCTION to get the other behavior.

There is a problem in both versions that WHERE clauses containing
no variables (table fields) will be assumed to be constants even
if they contain non-cachable function calls :-(. Thus, for example,
select * from foo where random() < 0.5
doesn't work as desired. I plan to fix this for 7.1.

Offhand I don't see a use for a nextval-like function in WHERE,
so you're probably safe with both 6.5 and 7.0.

regards, tom lane