Re: big distinct clause vs. group by

2011/4/23 Robert Haas <robertmhaas@gmail.com>

On Apr 18, 2011, at 1:13 PM, Uwe Bartels <uwe.bartels@gmail.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