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Re: Problem in age on a dates interval

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Theodore Petrosky <tedpet5(at)yahoo(dot)com>
Cc: Luis Sousa <llsousa(at)ualg(dot)pt>, pgsql-sql(at)postgresql(dot)org
Subject: Re: Problem in age on a dates interval
Date: 2004-07-16 14:34:07
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-sql
Theodore Petrosky <tedpet5(at)yahoo(dot)com> writes:
> wow.... at first I thought I had my head around a leap
> year problem so I advanced your query a year....

I think what's going on here is a difference of interpretation about
whether an "M months D days" interval means to add the months first
or the days first.  For instance

2005-02-18 plus 2 months = 2005-04-18, plus 24 days = 2005-05-12

2005-02-18 plus 24 days = 2005-03-14, plus 2 months = 2005-05-14

The timestamp-plus-interval operator is evidently doing addition the
first way, but it looks like age() is calculating the difference in a
way that implicitly corresponds to the second way.

I have some vague recollection that this has come up before, but
I don't recall whether we concluded that age() needs to be changed
or not.  In any case it's not risen to the top of anyone's to-do list,
because I see that age() still acts this way in CVS tip.

			regards, tom lane

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