Re: factorial function/phase out postfix operators?

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Tue, May 19, 2020 at 2:30 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Anyway, the bottom-line conclusion remains the same: let's make sure
>> we know what we'd do after getting rid of postfix ops, before we do
>> that.

> Well, I don't think we really need to get too conservative here.
> ... It seems to me that
> the first thing that we need to do here is get a deprecation notice
> out, so that people know that we're planning to break this.

No, I disagree with that, because from what I've seen so far it's
not really clear to me that we have a full solution to the AS
problem excepting only postfix ops. I don't want to deprecate
postfix ops before it's completely clear that we can get something
out of it. Otherwise, we'll either end up un-deprecating them,
which makes us look silly, or removing a feature for zero benefit.

Stephen's nearby proposal to deprecate only after a patch has been
committed doesn't seem all that unreasonable, if you're only intending
to allow one cycle's worth of notice. In particular, I could easily
see us committing a fix sometime this summer and then sticking
deprecation notices into the back branches before v13 goes gold.
But let's have the complete fix in hand first.

> I'm still interested in hearing what people think about hard-coding !
> as a postfix operator vs. removing postfix operators altogether. I
> think Vik and Tom are against keeping just !, Kenneth Marshall are for
> it, and I'm not sure I understand Pavel's position.

Yes, I'm VERY strongly against keeping just !. I think it'd be a
ridiculous, and probably very messy, backwards-compatibility hack; and the
fact that it will break valid use-cases that we don't need to break seems
to me to well outweigh the possibility that someone would rather not
change their queries to use factorial() or !!.

However, we do have to have a benefit to show those people whose
queries we break. Hence my insistence on having a working AS fix
(or some other benefit) before not after.

regards, tom lane