Re: [PATCH] Negative Transition Aggregate Functions (WIP)

Andres Freund <andres@2ndquadrant.com> writes:
> You'll have to handle adding negative values and underflow as
> well.

Right.

> Maybe it's instead sufficient to just have flag indicating that you're
> working with a state that hasn't overflowed so far and just plain int8
> math as long as that's the case, and entirely fall back to the current
> path once overflowed. That will probably be slightly faster and easily
> handle the majority of cases since overflowing int8 ought to be pretty
> rare in the real world.

Dunno, I think that a transition state containing both an int64 and
a (presumably separately palloc'd) numeric will be a real PITA.
And it will not be faster, because the principal drag on performance
will just be the overflow test, which you have to do either way.
        regards, tom lane