From: | Bruno Wolff III <bruno(at)wolff(dot)to> |
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To: | Elinor Medezinski <elinor(at)bellatrix(dot)tau(dot)ac(dot)il> |
Cc: | pgsql-novice(at)postgresql(dot)org, elinor(at)wise1(dot)tau(dot)ac(dot)il |
Subject: | Re: find close (duplicate) points + create index |
Date: | 2004-03-10 04:16:24 |
Message-ID: | 20040310041624.GB31629@wolff.to |
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Lists: | pgsql-novice |
On Thu, Mar 04, 2004 at 12:42:23 +0200,
Elinor Medezinski <elinor(at)bellatrix(dot)tau(dot)ac(dot)il> wrote:
> Hello,
>
> I have a table with one column --
> "CREATE TABLE pointtable (point POINT)".
> I'm trying to find duplicate entries, where two entries are considered
> duplicates if they're within a radius of 1, meaning something like ~ "select
> point from pointtable where distance between points <=1".
> Obviously this is not SQL syntax. Is there a way to do this - search within a
> column itself?
Yes, you can join a table to itself and return records matching some
critera. This isn't going to be fast. I didn't see a distance between
two points function, but it is probably there somewhere. If not you
can check if one point is contained in a circle of radius 1 centered
at the other point. This is something that could use an index, though
it probably wouldn't help when checking the whole table. It probably
would speed up checking a single point for conflicts.
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