Re: IMMUTABLE?

[Joachim Wieland <joe(at)mcknight(dot)de>]

On Tue, May 16, 2006 at 09:33:14AM -0400, Tom Lane wrote:
> Joachim Wieland <joe(at)mcknight(dot)de> writes:
> > So irrespective of caching to prevent evaluation across statements, within a
> > single statement, is there a strong reason why for example in
> > WHERE col = f(const) with f() declared as immutable or stable and without an
> > index on col, f() still gets called for every row? Or is this optimization
> > just not done yet?

> The above statement is not correct, at least not for immutable functions.

So an immutable function gets evaluated once but a stable function still gets
called for every row? Wouldn't it make sense to call a stable function only
once as well?


Joachim