Re: [SQL] Interval subtracting

From: Scott Marlowe <smarlowe(at)g2switchworks(dot)com>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Stephan Szabo <sszabo(at)megazone(dot)bigpanda(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Milen A(dot) Radev" <milen(at)radev(dot)net>, pgsql-sql(at)postgresql(dot)org, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [SQL] Interval subtracting
Date: 2006-03-01 20:36:37
Message-ID: 1141245396.18820.16.camel@state.g2switchworks.com
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-hackers pgsql-patches pgsql-sql

On Wed, 2006-03-01 at 14:27, Bruce Momjian wrote:
> Scott Marlowe wrote:
> > On Wed, 2006-03-01 at 14:18, Bruce Momjian wrote:
> > > Stephan Szabo wrote:
> > > > > 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.
> > > >
> > > > What about cases like interval '1 month -99 days', should that turn into
> > > > interval '-3 mons +21 days' or '-2 mons -9 days'?
> > >
> > > I think it should be the later. It is best to have a single sign, and I
> > > think it is possible in all cases:
> > >
> > > '2 mons -1 days'
> > >
> > > could be adjusted to '1 mons 29 days'.
> >
> > There's a part of me that thinks the WHOLE THING should be positive or
> > negative:
> >
> > -(2 months 1 day)
>
> But it isn't '-2 months, -1 day'. I think what you are saying is what I
> am saying, that we should make the signs consistent.

Pretty much. It just seems wrong to have different signs in what is
essentially a single unit.

We don't say 42 degrees, -12 minutes when measuring arc, do we? Then
again, maybe some folks do. It just seems wrong to me.

In response to

Responses

Browse pgsql-hackers by date

  From Date Subject
Next Message Mark Dilger 2006-03-01 20:39:30 Re: [SQL] Interval subtracting
Previous Message Tom Lane 2006-03-01 20:35:28 Re: [SQL] Interval subtracting

Browse pgsql-patches by date

  From Date Subject
Next Message Mark Dilger 2006-03-01 20:39:30 Re: [SQL] Interval subtracting
Previous Message Tom Lane 2006-03-01 20:35:28 Re: [SQL] Interval subtracting

Browse pgsql-sql by date

  From Date Subject
Next Message Mark Dilger 2006-03-01 20:39:30 Re: [SQL] Interval subtracting
Previous Message Tom Lane 2006-03-01 20:35:28 Re: [SQL] Interval subtracting