[pgrouting-users] Reduce the graph

[Aurélien FILEZ]

Hi,

This table is build with lines I decompose in segments of 2 points.

Maybe it is better to act from these full lines, searching points used by
more than one line ?

Thanks,
Kin

On Fri, Mar 9, 2012 at 5:48 PM, Stephen Woodbridge
<woodbri at swoodbridge.com>wrote:

> On 3/9/2012 11:39 AM, Aurélien FILEZ wrote:
>
>> Hi all,
>>
>> My edge table has some useless nodes. For example :
>>
>> edge_id    v1      v2      the_geom
>> 1              1        2      LINESTRING(x1 y1, x2 y2)
>> 2              2        3      LINESTRING(x2 y2, x3 y3)
>>
>> But the vertex 2 is no used in any other edge.
>>
>> So I would like reduce my graph to transforme this previous example to :
>> edge_id    v1      v2      the_geom
>> 1              1        3      LINESTRING(x1 y1, x2 y2, x3 y3)
>>
>> Is there is a way to do that ?
>>
>> Thank you all :)
>>
>
> There is no automatic way to do this. I have done a lot of graph analysis
> by adding a cnt column to the vertices_tmp column and then updating it to
> the count of edges connected to that vertex.
>
> Then you can do things like look for:
>
> deadends - cnt=1
> connected lines - cnt=2
>
> You could write a stored procedure to that the connected lines, join them
> together, and update the relevant tables to reflect the new topology.
>
> -Steve
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