Re: [PATCH] Optimize IS DISTINCT FROM NULL => IS NOT NULL

On Thu, Mar 8, 2012 at 19:35, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Uh ... how much do we care about that?  I can't say that I've heard many
> people complain about the fact that IS [NOT] DISTINCT FROM is poorly
> optimized -- which it is, in general, and this patch chips away at that
> only a tiny bit, not enough to make it recommendable.

Agreed, but it was very simple to code, so I figured why not.

> Plus I don't see why anyone would write the specific case
> "IS [NOT] DISTINCT FROM NULL" when they could write half as much.

Well I can see how it might be useful in generated queries, when
comparing a column to a parameter. If they're using IS DISTINCT FROM
then it's reasonable to expect that the parameter could be NULL
sometimes.

But I don't feel strongly about this, maybe it's not worth
complicating this big function further. :)

Regards,
Marti