Mark Dilger wrote:
Tom Lane wrote:
"Milen A. Radev" <[EMAIL PROTECTED]> writes:
Milorad Poluga напи�а:
SELECT '10 years 1 mons 1 days'::interval - '9 years 10 mons 15
days'::interval
?column? --------------- 3 mons -14 days
Why not '2 mons 16 days' ?
Please read the last paragraph in section 8.5.1.4 of the manual
(http://www.postgresql.org/docs/8.1/static/datatype-datetime.html#AEN4775)
. It mentions the functions named "justify_days" and "justify_hours"
that could do what you need.
justify_days doesn't currently do anything with this result --- it
thinks its charter is only to reduce day components that are >= 30 days.
However, I think a good case could be made that it should normalize
negative days too; that is, the invariant on its result should be
0 <= days < 30, not merely days < 30. Similarly for justify_hours.
Comments anyone? Patch anyone?
Sure, if nobody objects to this change I can write the patch.
mark
I've modified the code and it now behaves as follows:
select justify_days('3 months -12 days'::interval);
justify_days
----------------
2 mons 18 days
select justify_days('3 months -33 days'::interval);
justify_days
---------------
1 mon 27 days
select justify_hours('3 months -33 days -12 hours'::interval);
justify_hours
---------------------------
3 mons -34 days +12:00:00
select justify_days(justify_hours('3 months -33 days -12 hours'::interval));
justify_days
------------------------
1 mon 26 days 12:00:00
select justify_hours('-73 hours'::interval);
justify_hours
-------------------
-4 days +23:00:00
select justify_days('-62 days'::interval);
justify_days
------------------
-3 mons +28 days
I find the last two results somewhat peculiar, as the new functionality pushes
the negative values upwards (from hours to days, days to months). Changing '-73
hours' to '-3 days -1 hour' might be more intuitive? The '-4 days +23 hours' is
however consistent with the behavior in the other cases.
Thoughts? I will package this up into a patch fairly soon.
mark
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