[pgrouting-users] pgr_createTopology

Stephen Woodbridge woodbri at swoodbridge.com
Sat Nov 30 11:46:47 PST 2013

On 11/30/2013 2:18 PM, Stephen Mather wrote:
> Is pgr_createTopology deterministic in how it numbers nodes in a built
> topology?


What do you mean by this?

If you build a topology on the same edge table twice, do we guarantee 
that the nodes numbers will be identical?

I think the answer is NO, on line:303 of 
src/common/sql/pgrouting_topology.sql there is no "order by" clause. 
This would need to be added to make it deterministic because relational 
set theory does not guarantee order of records in a query without 
explicitly including and "order by" clause.

Write a bug if you think this is needed and state why.


More information about the Pgrouting-users mailing list