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List:       postgis-users
Subject:    Re: [postgis-users] spatial extents of a PostGIS db
From:       Kevin Neufeld <kneufeld () refractions ! net>
Date:       2010-03-24 16:36:35
Message-ID: 4BAA3F93.9050601 () refractions ! net
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On 3/24/2010 1:29 AM, Mike Toews wrote:
> Hi Paul,
> 
> To get the bounds for one layer/table, you need an aggregate
> (ST_Collect) and envelope on the aggregate. For one layer/table, it
> would look something like:
> 
> SELECT ST_AsText(ST_Envelope(ST_Collect(the_geom)))  AS envelope FROM mylayer;
> 

Sorry, Mike, but I don't think you want to do this.
As an example, I have a linear table of 18 million records spanning about 12GB of \
data.  Your solution will try to  create a single geometry from the entire collection \
(a single 12GB geometry object) and then take the envelope of it.

Rather, as Debasish Sahu suggested, use ST_Extent \
(http://postgis.refractions.net/docs/ST_Extent.html).

Cheers,
Kevin
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