Re: BUG #1993: Adding/subtracting negative time intervals

Andrew - Supernews wrote:
> On 2005-10-26, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > Andrew - Supernews <andrew+nonews(at)supernews(dot)com> writes:
> >> Um, what? Under what conditions is it permissable for simple arithmetic on
> >> (only) timestamptz values (which may have originated in different timezones
> >> neither of which is the current one) to be dependent on the current timezone
> >> setting?
> >
> > Timestamp subtraction will give different answers depending on whether
> > there's a DST adjustment in between.
>
> no, it _WILL NOT_.
>
> In your example, the result is different between timezones because the
> _input data_ is different. '2005-10-31'::timestamptz designates a different
> time in US/Eastern than it does in Japan, or UTC, or whatever.
>
> Or to put it in terms of the code: in 8.0, timestamptz_in is stable
> rather than immutable (since it depends on timezone), while timestamptz_mi
> is immutable (result depends only on the input values).
>
> In 8.0, I'm guaranteed that for timestamptz values, a+(b-a) = b in all
> cases regardless of timezone. 8.1 has broken that.

Yes, that is a valid problem, but what solution do we have at this
stage?

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