Re: Patch for SQL-Standard Interval output and decoupling DateStyle from IntervalStyle

I wrote:
> ... Consider

>     -1 1:00:00        flips the sign
>     - 1 1:00:00        doesn't flip the sign
>     -1 day 1:00:00        doesn't flip the sign
>     -2008-10 1:00:00    flips the sign
>     -2008-10 1        doesn't flip the sign
>     -2008 years 1:00:00    doesn't flip the sign

> If the rule were that it never flipped the sign for non-SQL-spec input
> then I think that'd be okay, but case 4 here puts the lie to that.
> I'm also not entirely sure if case 2 is allowed by SQL spec or not,
> but if it is then we've got a problem with that; and even if it isn't
> it's awfully hard to explain why it's treated differently from case 1.

Actually case 2 is a red herring --- I now see that ParseDateTime()
collapses out the whitespace and makes it just like case 1.  So never
mind that.  Case 4 is still bogus though.
        regards, tom lane