Re: Inlining functions with "expensive" parameters

Andres Freund <andres@anarazel.de> writes:
> Well, it's not a question of cost of the function now? Imagine
>     SELECT inlineable(something());
> if you have 10 references for the parameter inside inlineable(). Then
> currently something() would be evaluated 10 times. Which'd quite
> possibly be bad.

Right.  I kind of thought we only worried about that if the parameter
was referenced more than once, but I might be wrong.

> But what I *am* wondering about, is why we're not handling the
> parameters in a different way. Instead of replacing the all parameter
> references with the parameter, it shouldn't be too hard to instead
> replace them with a new PARAM_EXEC like Param.

Yeah, there's no mechanism like that now, but there could be.  I wonder
if we could connect that to the work that was being done for caching
nonvolatile subexpressions --- it feels like much the same problem.
        regards, tom lane