On Mon, Nov 10, 2014 at 10:07 AM, Ilya Ashchepkov <koctep@xxxxxxxxx> wrote:
Is this correct?
$ select
justify_interval(t-f-i)
,t-f-i
from
(
select
timestamp '2014-1-1' as f,
timestamp '2015-1-1' as t,
interval '06:49:00' as i
) S;
justify_interval | ?column?
------------------------+--------------------
1 year 4 days 17:11:00 | 365 days -06:49:00
Why do we have 360 days in a year?
Seems to be, the docs says:
justify_days(interval) |
interval | Adjust interval so 30-day time periods are represented as months | justify_days(interval '35 days') | 1 mon 5 days |
justify_hours(interval) |
interval | Adjust interval so 24-hour time periods are represented as days | justify_hours(interval '27 hours') | 1 day 03:00:00 |
justify_interval(interval) |
interval | Adjust interval using justify_days and justify_hours, with additional sign
adjustments |
justify_interval(interval '1 mon -1 hour') | 29 days 23:00:00 |
And, IIRC, an interval stores 3 parts, months, days and secods. The 365 days are justified to 12 months 5 days by justify days, then the 5 days - 6:49:0 are justified to 4 days 17:11:00 and then the 12 months are printed as 1 year ( because months are printed as MM/12 years, MM%12 months ).
What I'm not sure is why the right column is stated as 365 days minus six hours and change instead of 1 year minus six hours, maybe testing the parts in sequence may shed light on it, but I wouldn't rely on justify_xxx for any precise thing on big intervals given it's definition ( unless you are working only with intervals and using 30 days months, 24 hour days exclusively ).
Francisco Olarte.
