[postgis-users] Adding a new GEOS call to PostGIS

Paul Ramsey pramsey at refractions.net
Tue Feb 12 07:07:20 PST 2008

OK, it was a bit harder than you interpreted (takes more than a SQL  
cut'n'paste) and not as straightforward as I thought it might be (the  
simplify function that was already there was a native implementation,  
not a GEOS call, so cutting and pasting it would do no good).

Anyhow, I have applied my incredible text editing skills and now there  
is a ST_SimplifyPreserveTopology(geometry, float) in the -svn drop.


On Feb 8, 2008, at 10:21 PM, Brian Hamlin wrote:

> It recently came up in the IRC channel FreeNode #postgis
> that there is a GEOS TopologyPreserveSimplify, in addition
> to Simplify2D.
> I did a bit of checking just now.. on my machine, I see
> nm /usr/local/pgsql/lib/liblwgeom.1.3.so
> _LWGEOM_simplify2d
> _pg_finfo_LWGEOM_simplify2d
> _simplify2d_lwgeom
>   and some others, but no TopologyPreserve anything
> nm /usr/lcoal/lib/libgeos_c.1.4.1.dylib
> _GEOSSimplify
> _GEOSTopologyPreserveSimplify
> and lastly, in lwpostgis.sql
>  CREATE OR REPLACE FUNCTION simplify(geometry, float8)
>    RETURNS geometry
>    AS '$libdir/liblwgeom', 'LWGEOM_simplify2d'
> --
> since the last SQL line matches the exported symbol name from  
> liblwgeom
> exactly, minus the front _, looks like there is the exact entry point.
> Clearly no parallel entry for TopologyPreseveSimplify
> this makes me think that there is a little more to adding the call to
> lwpostgis.sql than copying and pasting the declaration.
> insights welcome
>   -Brian
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