Re: NULL-handling in aggregate(DISTINCT ...)

Andrew Gierth <andrew@tao11.riddles.org.uk> writes:
> "Tom" == Tom Lane <tgl@sss.pgh.pa.us> writes:
>  Tom> I think you could probably just change it: make DISTINCT work as
>  Tom> per regular DISTINCT (treat null like a value, keep one copy).
>  Tom> All the spec-conforming aggregates are strict and would ignore
>  Tom> the null in the next step anyway.

> Change it for single-arg DISTINCT too? And the resulting change to the
> established behaviour of array_agg is acceptable? Just want to be clear
> here.

I doubt that very many people are depending on the behavior of
array_agg(DISTINCT); and anyway it could be argued that the present
behavior is a bug, since it doesn't work like standard DISTINCT.
I don't see a problem with changing it, though it should be
release-noted.
        regards, tom lane