Re: Useless sort by

Gaetano Mendola <mendola@gmail.com> writes:
> because of that sort in the view definition the first query above
> takes not less than 3 seconds. I have solved this performance issue
> removing the sort from the view definition and putting it in the
> select reducing the time from > 3secons to < 150ms.

> Can not the optimizer take rid of that useless sort on those
> kind of queries ?

It is not the optimizer's job to second-guess the user on whether a sort
is really needed there.  If we did make it throw away non-top-level
sorts, we'd have hundreds of users screaming loudly.

            regards, tom lane