Re: [PATCH] Generate random dates/times in a specified range

From: Greg Sabino Mullane <htamfids(at)gmail(dot)com>
To: Damien Clochard <damien(at)dalibo(dot)info>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: [PATCH] Generate random dates/times in a specified range
Date: 2025-07-12 15:14:43
Message-ID: CAKAnmmKDBEPcsAsy=PHCqOnqT+8cHSCghPkKLJuBACcF+yggnQ@mail.gmail.com
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Patch review

OVERALL:

I like the idea, especially the date variant. Unlike Tom, I'm not
particularly concerned about breakage of existing scripts, as
most already are working just fine with raw numbers and I don't see this
patch breaking them.

In a selfish vein, I would use the "date" and timestamp variants a lot. I
would use the "time" ones seldom to never.

HOUSEKEEPING:

* Needs a pgindent run

* Commit message typo: developped

DOCS:

* Suggest adding an example of a random(date, date) call at the end of the
<row> section

* Typo: speficy

* Suggest: "current session's timezone"

* Suggest: remove "instead"

CODE:

* Code comments should be consistent with "Returns" not "Generate"

* result = (DateADT) (int32) pg_prng_int64_range(&prng_state, rmin, rmax);

Is the int32 cast needed here? My compiler seems fine without it

* This behaviour is based on generate_series_timestamptz_internal

Is it? I'm not seeing much overlap between the two

The addition of a timezone arg does complicate things. Is it really needed?

If not (just relying on session), timetzrandom becomes much much simpler
(e.g. time_timetz)

RUNNING:

* Found a bug:

greg=# select random('12:00'::time, '13:00'::time);
random
-----------------
12:41:35.612385

greg=# select random('12:00'::time, '13:00'::time, ''::text);
random
--------------------
12:20:58.308452-04

greg=# select random('12:00'::time, '13:00'::time, 'FOO'::text);
ERROR: time zone "FOO" not recognized

greg=# select random('12:00'::time, '13:00'::time, 'IST-9'::text);
random
--------------------
12:42:46.384039+09

greg=# select random('12:00'::time, '13:00'::time, 'IST'::text);
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.

At the very least, add a simple TLA timezone to the sql tests once fixed.

* Infinity

Fun, but is it useful? Perhaps disallow infinity. No strong opinion on this.

greg=# select random(now(), 'infinity'::date);
random
--------------------------------
86609-03-21 15:23:43.291271-04

greg=# select random('-infinity'::date, 'infinity'::date);
random
---------------
6126327-09-13

Cheers,
Greg

--
Crunchy Data - https://www.crunchydata.com
Enterprise Postgres Software Products & Tech Support

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