[postgis-devel] [PostGIS] #1195: CopyTopologyLayer

PostGIS trac at osgeo.org
Tue Oct 11 00:19:34 PDT 2011

#1195: CopyTopologyLayer
 Reporter:  robe         |       Owner:  strk         
     Type:  enhancement  |      Status:  new          
 Priority:  medium       |   Milestone:  PostGIS 2.0.0
Component:  topology     |     Version:  trunk        
 Keywords:               |  

Comment(by strk):

 No tables exist but relations do. The relations table is like a collection
 of TopoGeometry objects (the full definition is available there, and
 strictly coupled with the primitives in that specific topology).

 If we drop them, we drop a full level of abstraction built on the
 We keep the primitives but loose the higher level.

 About what to do: if you know which TopoGeometry id has which attributes,
 you may re-link the TopoGeometry to its attributes. For example you may
 add a new topogeometry column to an existing table (the source topology
 layer) to point to the copy. This may be useful, in turn, to have a
 simplified version of the same topology layer.

 An additional argument to CopyTopology to avoid the copy of the
 TopoGeometry definitions might be a good idea, since you have use cases
 for that.

 What would CopyTopologyLayer do exactly ? It'll need to copy the
 primitives to a new topology I guess ? If you call the function on
 multiple layers, sharing the same primitives, what will happen ?

 What I've been thinking about was more along the lines of making it easier
 to re-link orphaned TopoGeometry to actual tables. Because you should be
 able to easily add a TopoGeometry field and set it to old TopoGeometry
 with just topology id changed, but probably NOT that easily and surely NOT
 usin the AddTopoGeometryColumn function, which would insist on adding rows
 in topology.layer which you already have available.

Ticket URL: <http://trac.osgeo.org/postgis/ticket/1195#comment:1>
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