[postgis-devel] Rant on SRID -1 vs 0

[Stephen Woodbridge]

bborie,

Thanks, these are helpful suggestions.

On 7/15/2013 5:36 PM, Bborie Park wrote:
> Stephen,
>
> I can't say much about the behavior changes for ST_StartPoint() and
> ST_GeometryN() but for SRID, you should try...
>
> SELECT ST_SRID('POINT(0 0)'::geometry)
>
> That will always give you the correct unknown SRID value for whatever
> version of PostGIS. For your example...
>
> select addgeometrycolumn('unnoded', 'the_geom', ST_SRID('POINT(0
> 0)'::geometry), 'LINESTRING', 2);
>
> I forget but can't you just shove in -1 for SRID? PostGIS 2.0 should
> automatically clamp values < 0 to 0.

Yes this works, I was avoiding it because it raises an notice which 
messes with them test infrastructure.

Thanks,
   -Steve

> -bborie
>
>
>
> On Mon, Jul 15, 2013 at 2:23 PM, <maplabs at light42.com
> <mailto:maplabs at light42.com>> wrote:
>
>     I was around during this discussion..
>     (most respect to SWoodbridge and some empathy for the frustration..
>     but..)
>
>     2.0 was clearly a major change, with the binary format of geometry
>     first and foremost.. If there was any time to make a somewhat
>       arbitrary change like the "unassigned" value,
>     2.0 was arguably the best time to do it..
>
>     Personally, the zero value makes more sense to me, and I think I
>     said so at that time also
>     $0.02
>
>     --
>     Brian M Hamlin
>     OSGeo California Chapter
>
>
>     On Mon, 15 Jul 2013 17:10:51 -0400, Stephen Woodbridge
>     <woodbri at swoodbridge.com <mailto:woodbri at swoodbridge.com>> wrote:
>     I need to vent some frustration with the the change from srid=-1 to
>
>         srid=0 for the undefined projection because this totally breaks
>         scripts and makes it very hard to test things like pgrouting
>         that need to work on both 1.5, 2.0 and 2.1.
>         For example:
>
>         select addgeometrycolumn('unnoded', 'the_geom', 0, 'LINESTRING', 2);
>
>         does not work on  POSTGIS="1.5.3" GEOS="3.3.8-CAPI-1.7.8"
>         PROJ="Rel. 4.8.0, 6 March 2012" LIBXML="2.7.8" USE_STATS
>
>         And this is just the first of the problems I'm trying to track
>         down.
>         The second is the change in behavior of st_startpoint() with
>         multi geometries and the change of st_geometryn() with simple
>         geometry. This forces every function that uses these to check
>         the postgis version conditionally implement access.
>
>         Grummble, gummble, gummble, off to find some kind of solution(s).
>         -Steve
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