[postgis-devel] Found possible platform-specific bug in PostGIS 1.4.0 ?

[Mark Cave-Ayland]

Nathan Widmyer wrote:

> Attached are two psql sessions, one on a WinXP Pro SP3 machine, another 
> to Ubuntu Hardy 8.04.  (one pair of files have unix line endings, 
> another has DOS line endings, for your convenience).
> 
> There are 18 polygons in the data set and I want to make a union out of 
> them.  The union works in Linux but fails with an exception in Windows.
> 
> I received an error on the Windows box (TopologyException: found 
> non-noded intersection ...), then brought the data over to the linux box 
> for analysis, and curiously the operation worked.
> 
> If you visualize it, I think the last polygon (#18) shares a common line 
> segment in space with another (possibly #15), but breaks where #18 has a 
> vertex on the line of #15.
> However there are at least 2 polygons that cover the same point in space 
> so the point shouldn't even be a problem because it's not on the outside 
> of the resulting shape.
> 
> I'm sure my analysis is lacking, but wanted to communicate all I found out.
> Using an alternate strategy of linework does get the union shape though.
> 
> 
> Nathan

Hi Nathan,

Thanks for the analysis and test case. One of the key bits of 
information you forgot to include though was the version of PostGIS and 
PostgreSQL being used on each box. Can you post the output of the 
following on both boxes:

SELECT version();
SELECT postgis_full_version();


ATB,

Mark.

-- 
Mark Cave-Ayland - Senior Technical Architect
PostgreSQL - PostGIS
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