Re: Functional dependencies and GROUP BY

On Sat, Jul 17, 2010 at 04:15, Peter Eisentraut <peter_e(at)gmx(dot)net> wrote:
> On fre, 2010-07-16 at 22:29 -0600, Alex Hunsaker wrote:
>> The only corner case I have run into is creating a view with what I
>> would call an implicit 'not null' constraint.  Demonstration below:
>>
>> create table nn (a int4 not null, b int4, unique (a));
>> select * from nn group by a; -- should this work? I think not?
>
> I believe I referred to this upsthread.

Aww, and here I thought I had just been diligent :). In other news
its really no surprise that your test with 1600 columns had little
effect. As it loops over the the indexes, then the index keys and
then the group by items right? So I would expect the more indexes you
had or group by items to slow it down. Not so much the number of
columns. Right?

Anyhow it sounds like I should try it on top of the other patch and
see if it works. I assume it might still need some fixups to work
with that other patch? Or do you expect it to just work?