[postgis-devel] [PostGIS] #408: Catch "Exception in LWGEOM2GEOS" in ST_IsValid

strk strk at keybit.net
Thu Feb 4 13:30:09 PST 2010


I might be missing something, but wouldn't an exception 
from LWGEOM2GEOS mean unambiguosly that the geometry
is invalid ?

... thinkin loud ... could also be an OOM actually ...

--strk;

On Thu, Feb 04, 2010 at 01:26:38PM -0800, Martin Davis wrote:
> Right, this has just been explained to me by our resident PostGIS expert 
> Kevin.  To repeat his explanation, the PostgreSQL language engine is 
> auto-converting the string to a Geometry type, since that's what 
> st_isvalid accepts.  This is where the exception is happening - which 
> means that it can't be caught inside st_isvalid.
> 
> I would humbly suggest that it would be nice to be able to prevent C 
> exceptions leaking out into the SQL world where possible. Perhaps a
> 
> st_isvalid_safe(String geomWKT)
> 
> could be provided to allow users to avoid this.  (And since Kevin also 
> pointed out that this doesn't allow distinguishing between Geometry and 
> the new Geography type, a
> 
> st_isvalid_geog_safe(String geogWKT)
> 
> might be needed as well.
> 
> Code it up and let the users vote with their keyboards!
> 
> PostGIS wrote:
> >#408: Catch "Exception in LWGEOM2GEOS" in ST_IsValid
> >--------------------------+-------------------------------------------------
> >  Reporter:  ddegasperi   |       Owner:  pramsey
> >      Type:  enhancement  |      Status:  new    
> >  Priority:  medium       |   Milestone:         
> > Component:  postgis      |     Version:  1.4.X  
> >Resolution:               |    Keywords:         
> >--------------------------+-------------------------------------------------
> >Comment (by pramsey):
> >
> > Non possible.
> >
> > The '':text entry first gets passed into the text parsing routines which
> > is where the failure actually occurs, not in st_isvalid. We have had
> > internal arguments many times about where validity checking should occur,
> > and the current situation is that trivially invalid geometries (1-point
> > lines, unclosed polygons) are failed during parsing.
> >
> > IMO, they shouldn't fail, but that's a personal opinion, not a consensus
> > one.
> >
> >  
> 
> -- 
> Martin Davis
> Senior Technical Architect
> Refractions Research, Inc.
> (250) 383-3022
> 
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