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

From: John Naylor <john(dot)naylor(at)enterprisedb(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Aleksander Alekseev <aleksander(at)timescale(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: mark the timestamptz variant of date_bin() as stable
Date: 2021-09-15 15:57:57
Message-ID: CAFBsxsE7_cjwzu1OvmMTRf+mLfpB3vLk3xunsK1MiDPVkWZVEA@mail.gmail.com
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On Wed, Sep 1, 2021 at 3:25 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> John Naylor <john(dot)naylor(at)enterprisedb(dot)com> writes:
> > On Wed, Sep 1, 2021 at 2:44 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> 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)
>
> Yeah, and then back to timestamptz if that's what you really need :-(
>
> > It's a bit unintuitive, though.
>
> Agreed. If we keep it like this, adding some documentation around
> the point would be a good idea I think.

Attached is a draft doc patch using the above examples. Is there anything
else that would be useful to mention?

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

Attachment Content-Type Size
v1-doc-date-bin-dst.patch application/octet-stream 1.6 KB

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