Re: [patch] bit XOR aggregate functions

ne 7. 3. 2021 v 10:36 odesílatel Vik Fearing <vik(at)postgresfriends(dot)org>
napsal:

> On 3/6/21 9:06 PM, David G. Johnston wrote:
> > On Saturday, March 6, 2021, David Fetter <david(at)fetter(dot)org> wrote:
> >
> >>
> >>>> SELECT BIT_XOR(b ORDER BY a, c)... /* works */
> >>>> SELECT BIT_XOR(b) OVER (ORDER BY a, c)... /* works */
> >>>> SELECT BIT_XOR(b) FROM... /* errors out */
> >>>
> >>>
> >>> Why would such an error be necessary, or even desirable?
> >>
> >> Because there is no way to ensure that the results remain consistent
> >> from one execution to the next without such a guarantee.
> >>
> >
> > Numerous existing aggregate functions have this behavior. Making those
> > error isn’t an option. So is making this a special case something we
> want
> > to do (and also maybe make doing so the rule going forward)?
>
> Aside from the fact that bit_xor() does not need this, I am opposed to
> it in general. It is not our job to make people write correct queries.
>

I cannot agree with the last sentence. It is questions about costs and
benefits, but good tool should to make warnings when users does some stupid
things.

It is important at this time, because complexity in IT is pretty high, and
a lot of users are not well trained (but well trained people can make
errors too). And a lot of users have zero knowledge about technology, So
when it is possible, and when it makes sense, then Postgres should be
simple and safe. I think it is important for renome too. It is about costs
and benefits. Good reputation is a good benefit for us too. Ordered
aggregation was designed for some purposes, and should be used, when it has
sense.

Regards

Pavel

--
> Vik Fearing
>
>
>