On Nov 10, 2011 9:26 PM, "Thom Brown" <thom@linux.com> wrote:
>
> On 10 November 2011 13:05, Sorin Dudui <sd@wigeogis.com> wrote:
> > Hi,
> >
> >
> >
> > I have some functions that select data from tables which are daily or
> > monthly updated. My functions are marked as STABLE. I am wondering if they
> > perform better if I mark they as IMMUTABLE?
>
> No. IMMUTABLE is only appropriate when there is no access to table
> data from within the function
Sure it can be faster - the same way defining "fibonacci(int)" to always return 42 is faster, just incorrect.
You can sometimes kinda get away with it if you are willing to reindex, drop prepared statements, reload functions, etc when the result changes. I would not recommend it.