Re: mark the timestamptz variant of date_bin() as stable

On Wed, Sep 1, 2021 at 2:44 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> regression=# set timezone to 'America/New_York';
> SET
> regression=# select date_bin('1 day', '2021-11-01 00:00
+00'::timestamptz, '2021-09-01 00:00 -04'::timestamptz);
> date_bin
> ------------------------
> 2021-10-31 00:00:00-04
> (1 row)
>
> regression=# select date_bin('1 day', '2021-11-10 00:00
+00'::timestamptz, '2021-09-01 00:00 -04'::timestamptz);
> date_bin
> ------------------------
> 2021-11-08 23:00:00-05
> (1 row)
>
> I see that these two answers are both exactly multiples of 24 hours away
> from the given origin. But if I'm binning on the basis of "days" or
> larger units, I would sort of expect to get local midnight, and I'm not
> getting that once I cross a DST boundary.

Hmm, that's seems like a reasonable expectation. I can get local midnight
if I recast to timestamp:

# select date_bin('1 day', '2021-11-10 00:00 +00'::timestamptz::timestamp,
'2021-09-01 00:00 -04'::timestamptz::timestamp);
date_bin
---------------------
2021-11-09 00:00:00
(1 row)

It's a bit unintuitive, though.

--
John Naylor
EDB: http://www.enterprisedb.com