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Re: Comments on Exclusion Constraints and related datatypes

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Simon Riggs" <simon(at)2ndQuadrant(dot)com>
Cc: <pgsql-hackers(at)postgresql(dot)org>,"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: Comments on Exclusion Constraints and related datatypes
Date: 2010-03-22 16:01:52
Message-ID: 4BA74E20020000250003005A@gw.wicourts.gov (view raw or flat)
Thread:
Lists: pgsql-hackers
Simon Riggs <simon(at)2ndQuadrant(dot)com> wrote:
 
> Yes, for most people touching != overlap. So it just looks like a
> bug.
 
A quick search of the web turned up a definition of overlap in
geometry as meaning that two polygons share at least one *internal*
point, which would be consistent with your interpretation; but there
is the issue of breaking existing code.  Perhaps people are now
accustomed to following the existing overlaps test with a test that
the area of intersection is non-zero?
 
Anyway, based on what I found, we should document the current
behavior, as the term in PostgreSQL doesn't seem to match the
conventional definition in geometry.
 
-Kevin

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