Re: SUM(int2)/SUM(int4) do not detect overflow of the int8 accumulator

On 02/09/2026 09:37, Michael Paquier wrote:
> On Wed, Sep 02, 2026 at 08:01:56AM +0200, Andrei Lepikhov wrote:
>> In my mind, we should pay for CPU cycles only in practical cases. So, if this
>> case deserves an overflow check, it should be an assertion that consumes no
>> resources in production.
>
> All the patterns you are showing imply direct function calls, which
> don't really seem worth bothering about. Are any of these overflow
> cases reachable using operators with dedicated casts? I would count
> as OK even cases where the sum functions are used in a custom
> aggregate, say with a SFUNC set to one of the paths you are pointing
> at.
I use direct calls mainly to make regression tests run faster.

The first case arose during benchmarking built-in SUM(int4) with various
parallelising methods [1] (bare research topic) at scale. This may not be a big
issue right now, but as databases get larger, it could become one. I think it's
more likely to happen first in the microcurrency space, where the base unit is a
cent instead of a dollar, especially with very large partitioned tables.

[1] https://www.pgedge.com/blog/do-global-hash-tables-strike-back-in-postgresql

--
regards, Andrei Lepikhov,
pgEdge