Re: BUG #17496: to_char function resets if interval exceeds 23 hours 59 minutes

At Thu, 14 Jul 2022 17:57:32 -0400, Bruce Momjian <bruce@momjian.us> wrote in 
> On Tue, May 24, 2022 at 01:11:45PM -0700, Nathan Bossart wrote:
> > The documentation for this function indicates HH24 can output hour values
> > higher than 23∴
> > 
> >         <function>to_char(interval)</function> formats <literal>HH</literal> and
> >         <literal>HH12</literal> as shown on a 12-hour clock, for example zero hours
> >         and 36 hours both output as <literal>12</literal>, while <literal>HH24</literal>
> >         outputs the full hour value, which can exceed 23 in
> >         an <type>interval</type> value.
> > 
> > I see different results depending on how I define the interval:
> > 
> >     postgres=# select to_char(INTERVAL '1 day', 'HH24:MI');
> >      to_char 
> >     ---------
> >      00:00
> >     (1 row)
> > 
> >     postgres=# select to_char(INTERVAL '24h', 'HH24:MI');
> >      to_char 
> >     ---------
> >      24:00
> >     (1 row)
> > 
> > The example provided is more like the former (no hour value), because
> > "timestamp - timestamp" converts 24-hour intervals into days.  In general,
> > I agree that this probably not a bug.  You probably want to ask to_char()
> > to display the days as well..

On the other hand, "interval + interval" doesn't convert hours into
days. I expected the math to do normalization.

select INTERVAL '1 day 15hour' + interval '2 day 15 hour';
    ?column?     
-----------------
 3 days 30:00:00

Is there any means to control over normalization?

> select normalize_interval('3 days 30:00:00'::interval, 'HH24:MI')
> 102:00
> select normalize_interval('3 days 30:00:00'::interval, 'DD HH24:MI')
> 4 04:00
> select normalize_interval('3 days 30:00:00'::interval, 'HH12:MI')
> ERROR:  hours out of range


> Well, if we did that then this would be odd:
> 
>     SELECT to_char(INTERVAL '2 day', 'DD HH24:MI');
>      to_char
>     ----------
>      02 00:00
> 
> or this:
> 
>     SELECT to_char(INTERVAL '2 day 4 hours', 'DD HH24:MI');
>      to_char
>     ----------
>      02 04:00

Mmm. I don't see this is odd...

-- 
Kyotaro Horiguchi
NTT Open Source Software Center