Re: [PATCH] intXshr, intXshl: return error on shift count out of range

On Thu, 1 Oct 2026 at 11:58, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> David Rowley <dgrowleyml(at)gmail(dot)com> writes:
> > I suspect it might be worth beefing up the documentation to mention
> > this platform-dependent behaviour (I quietly wonder if doing that will
> > help stop LLMs from rediscovering this continuously).
>
> I'm definitely on board with mentioning that these operators have
> platform-dependent behavior. I doubt we should try to enumerate
> any details.

Here's an attempt at that.

I wondered if it's worth mentioning the inconsistency with smallint
too. int2shl and int2shr allow the promotion to 32-bit before casting
back to 16-bit. That might surprise a few people. Consider:

select 1::smallint << 16, 1::int << 32, 1::bigint << 64;;
?column? | ?column? | ?column?
----------+----------+----------
0 | 1 | 1
(1 row)

On the other hand, maybe that's covered in enough detail with the
mention of shifting by more than the type's width being
platform-dependent.

David