(using postgresql 6.5.2)
I have created a set of postgres extension functions in C (which use SPI
to perform queries), and added them to my database with something like
this:
CREATE FUNCTION my_next_uid(text) RETURNS text AS '/usr/lib/pgsql/my_uids.so' LANGUAGE 'c';
My functions are designed to behave like nextval() and friends, except
that they operate on a varchar field in a predetermined table, rather than
a database sequence. For example, my_next_uid() should always return a
unique value, incrementing the current value in said table each time it is
called.
So far, my functions appear to work correctly. However, looking at their
entries in the pg_proc table, I see that their "proiscachable" fields are
set to true. This worries me, because my understanding is that postgres
will re-use values returned by cachable functions, which is undesirable.
(In order for my_next_uid() to be useful, it must retrieve a new value
each time it is used.)
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.
Regards,
Forest Wilkinson