[postgis-users] Select polygons within polygon with PostGIS 2.0

[Sandro Santilli]

On Mon, Oct 15, 2012 at 11:37:08AM +0000, Astrid Bjørnerød wrote:
> No, I have really not understood  the way to get a link between the relation-table and the originally geo-table.

A TopoGeometry object represents that link.

> I have a table geoTable.
> All I want is to make query which returns the values of left and right polygons, like this :
>   Update geoTable set newValue = leftFace.value  where geoTable.field1 is null;  --if leftFace.Area > rightFace.Area or
>   Update geoTable set newValue = rightFace.value where geoTable.field1 is null; --if leftFace.Area < rightFace.Area
> 
> What is the mapping between myTopo.relation element_id and the geoTable and how do I get this (which topology functions)?

You only want to query the relation table to know the composition
of your TopoGeometry. In your case this would probably be a list
of face identifiers. But you can also use functions to get that
information: GetTopoGeomElementArray or GetTopoGeomElements.

You ask:

 "[..] I want [..] the values of left and right polygons"

Left and right of what ? In the topology model we refer to 
"left" and "right" of an edge. Is that what you're looking for ?

--strk;

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