Subtracting Two Intervals

Terry Lee Tucker wrote:

In porting from 7.4.19 to 8.3.1 I have found the following:

7.4.19:
mwr=# select interval '1 day 15 hours 30 minutes' - interval '29 hours';
?column?
--------------------
@ 10 hours 30 mins
(1 row)

8.3.1:
mwr83=# select interval '1 day 15 hours 30 minutes' - interval '29 hours';
?column?
----------------------------
@ 1 day -13 hours -30 mins
(1 row)

Is that right? I mean if you take 1 day (24 hours) and add -13 hours and -30
minutes, you get 10 hours and 30 minutes, but is it supposed to display that
way?

We removed assumptions that every day is 24 hours between those
releases. You can use justify_hours() to get the proper result:

test=> select justify_hours(interval '1 day 15 hours 30 minutes' -
interval '29 hours');
justify_hours
---------------
10:30:00
(1 row)

There have been good arguments that justify_hours() behavior should be
the default.

--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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