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Re: Comments on Exclusion Constraints and related datatypes

From: David Fetter <david(at)fetter(dot)org>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>,Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Comments on Exclusion Constraints and related datatypes
Date: 2010-03-22 16:00:28
Message-ID: 20100322160028.GB26428@fetter.org (view raw or flat)
Thread:
Lists: pgsql-hackers
On Mon, Mar 22, 2010 at 03:42:39PM +0000, Simon Riggs wrote:
> On Mon, 2010-03-22 at 10:32 -0500, Kevin Grittner wrote:
> > Simon Riggs <simon(at)2ndQuadrant(dot)com> wrote:
> > > On Mon, 2010-03-22 at 10:13 -0400, Tom Lane wrote:
> > >> Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> >  
> > >> > * Circles, Boxes and other geometric datatypes defined
> > >> > "overlaps" to include touching shapes. So SELECT circle
> > >> > '((0,0), 1)' && circle '((2,0),1)'; is true, which is fairly
> > >> > strange and makes those datatypes very counter intuitive.
> > >> > Considering they are instructional aids, this is bad.
> > >> 
> > >> You're approximately twenty years too late to propose changing
> > >> that, even if it were clearly a good idea which I doubt.
> > > 
> > > Possibly. We should at least document that.
> >  
> > Basically, what you feel is missing is documentation that if two
> > shapes share one or more points they are considered to overlap;
> > there is no requirement that they share an area?
> 
> Yes, for most people touching != overlap. So it just looks like a
> bug.

I don't know which people you've surveyed, but at least in my math
classes, one point in common was sufficient for an overlap.  I'd be
happy to write up something that makes this clear.

Cheers,
David.
-- 
David Fetter <david(at)fetter(dot)org> http://fetter.org/
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Subject: Re: Comments on Exclusion Constraints and related datatypes
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