[postgis-users] Using a rectangular selection

[Henri De Feraudy]

What you probably mean is that a query like Select geom from mytable where ST_Intersects(geom,my_rectangular_selection) is very efficient, right?Do I have to be careful to create indexes, or is that done automatically when I add a geometrical column?


--- On Tue, 11/24/09, Brian Modra <epailty at googlemail.com> wrote:

From: Brian Modra <epailty at googlemail.com>
Subject: Re: [postgis-users] Using a rectangular selection
To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
Date: Tuesday, November 24, 2009, 5:00 AM

2009/11/23 Henri De Feraudy <feraudyh at yahoo.com>
>
> Hi,
>   I'm working in planar coordinates. I have a Postgis database and
> for starters I want to limit my attention to all geometries that intersect a given rectangle (the "selection").
> I can imagine that one could enumerate all geometries and ask in each case if they
> intersect the rectangle, but that doesnt seem very efficient, so what do you suggest?

Use ST_Intersects

> I only need general guidance so I can look at the various parts of the doc.
> Later I'll be wanting to clip the geometies with this selection.
> Still later I'll want to consider polygonal selections.
> By the way I'm accessing the PostGis database via LibPQ and have written my application
> in Qt.
>
> Thanking you in advance
> Henri
>
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