Getting a leading zero on negative intervals with to_char?

[Craig Ringer <ringerc@xxxxxxxxxxxxx>]

Hi all

I'm wondering if there's any way to convince `to_char` to add a leading zero to the hours in negative intervals. The current behaviour feels wrong, in that FMHH24:MM and HH24:MM produce the same output for negative intervals:

regress=# WITH x(i) AS (VALUES (INTERVAL '9:00'),(INTERVAL '-9:00'),(INTERVAL '11:00'),(INTERVAL '-11:00'),(INTERVAL '101:00'),(INTERVAL '-101:00') )
SELECT i as "interval", to_char(i,'HH24:MM') as "HH24:MM", to_char(i,'FMHH24:MM') AS "FMHH24:MM" FROM x;
  interval  | HH24:MM | FMHH24:MM
------------+---------+-----------
 09:00:00   | 09:00   | 9:00
 -09:00:00  | -9:00   | -9:00
 11:00:00   | 11:00   | 11:00
 -11:00:00  | -11:00  | -11:00
 101:00:00  | 101:00  | 101:00
 -101:00:00 | -101:00 | -101:00
(6 rows)

I can't find any way to produce the output '-09:00' . There's no apparent way to add an additional width-specifier. HH24 is clearly not constrained to be 2 digits wide, since "-11" and "101" and "-101" are all output by "HH24". It seems like "-9" should be "-09" with the HH24 specifier, and "-9" with the "FMHH24" specifier.

Opinions?

Unless I'm doing something woefully wrong, Oracle compatibility doesn't seem to be an issue because we format intervals wildly differently to Oracle anyway:

    http://sqlfiddle.com/#!4/d41d8/2751

and it looks like Oracle handling of intervals isn't much like Pg anyway:

    http://stackoverflow.com/questions/970249/format-interval-with-to-char


Arose from trying to find a non-ugly solution to this SO post:

    http://stackoverflow.com/questions/12335438/server-timezone-offset-value/12338490#12338490

--
Craig Ringer