[pgrouting-users] pgr_createTopology

Stephen Mather stephen at smathermather.com
Sat Nov 30 11:52:34 PST 2013

Cool, I'll write a ticket.  It would be mostly useful in the case of e.g.
tutorial development.


On Sat, Nov 30, 2013 at 2:46 PM, Stephen Woodbridge <woodbri at swoodbridge.com
> wrote:

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