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

Heikki Linnakangas <hlinnakangas@vmware.com> writes:
> I propose that we reimplement sum(bigint) in a more efficient way: For 
> the internal state, let's use an int8 and a numeric overflow field. The 
> transition function adds to the int8 variable, and checks for overflow. 
> On overflow, increment the numeric field by one. In the final function, 
> multiply the numeric by 2^64, and add the residual int8 value.

It'd probably be sufficient to handle it as two int64 fields (handmade
128-bit arithmetic, or maybe even not so handmade if that ever gets
reasonably common among C compilers).  You're assuming the final output
is still numeric, right?
        regards, tom lane