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

[Bborie Park]

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.

-bborie



On Mon, Jul 15, 2013 at 2:23 PM, <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> 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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>>
>>
>>
>
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