Re: big distinct clause vs. group by

2011/4/23 Robert Haas <robertmhaas(at)gmail(dot)com>

> On Apr 18, 2011, at 1:13 PM, Uwe Bartels <uwe(dot)bartels(at)gmail(dot)com> wrote:
> > Hi Robert,
> >
> > thanks for your answer.
> > the aggregate function I was talking about is the function I need to use
> for the non-group by columns like min() in my example.
> > There are of course several function to choose from, and I wanted to know
> which causes as less as possible resources.
>
> Oh, I see. min() is probably as good as anything. You could also create a
> custom aggregate that just always returns its first input. I've occasionally
> wished we had such a thing as a built-in.
>
>
I've once done "single" grouping function - it checks that all it's input
values are equal (non-null ones) and returns the value or raises an error if
there are two different values.

Best regards, Vitalii Tymchyshyn

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Best regards,
Vitalii Tymchyshyn