Re: Optimizer picks an ineffient plan

Well, it's unfortunate that you feel that way, because SQL Server handles it
correctly.

"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote in message
news:4375(dot)1062643465(at)sss(dot)pgh(dot)pa(dot)us(dot)(dot)(dot)
> Greg Stark <gsstark(at)mit(dot)edu> writes:
> > "Bupp Phillips" <hello(at)noname(dot)com> writes:
> >> select * from customer order by customer_id, first_name;
> >> [ where customer_id is the primary key ]
>
> > However you do have a point. In this case I don't think postgres even
> > considers using the index.
>
> It will not, since the index does not appear to provide the correct sort
> order.
>
> > However I'm not sure I see a lot of cases where this would come up.
>
> Yes, that's the real crux of the matter. Should the optimizer spend
> cycles on *every* query to detect cases where the user has written
> useless sort keys? I've got grave doubts that it's a win. ISTM such
> an optimization penalizes the folk who write their queries well to
> benefit those who are careless.
>
> regards, tom lane
>
> ---------------------------(end of broadcast)---------------------------
> TIP 8: explain analyze is your friend
>