On Thu, May 04, 2006 at 01:13:20 -0400, Tom Lane <[EMAIL PROTECTED]> wrote: > > I think it's a fair point that we could allow "SELECT DISTINCT x ORDER BY > foo(x)" if foo() is stable, but that does not imply that sorting by x is > interchangeable with sorting by foo(x). foo = abs is a trivial > counterexample.
I misunderstood Greg's example. Sorting by (foo(x), x) is a suitable replacement for sorting by foo(x). So that it would be OK to rewrite SELECT DISTINCT x ORDER BY foo(x) as SELECT DISTINCT ON (foo(x), x) x ORDER BY foo(x) Whether or not this is worthwhile to automate, I am not in a good position to judge. ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
