[postgis-devel] UnknownSRID value: 0 or -1 ?

[Sandro Santilli]

On Fri, Dec 09, 2011 at 10:03:52AM -0800, dustymugs wrote:
> On 12/09/2011 09:35 AM, Sandro Santilli wrote:
> >I've started work on testing dump/restore procedure for getting to 2.0
> >and realized the data w/out a proper SRID won't come back due to
> >ensure_srid_geom checks on tables insisting of the SRID being -1
> >rather than 0.
> >
> >There's no much we can do to fix this, unless we're willing to
> >drop the constraints from the user dump.
> >
> >For this reason I think it would be safer to get our unknown
> >srid back to -1 before it's too late (srid=0 getting in dumps
> >and making things even harder).
> >
> >If somebody has smarter ideas I'm happy to listen to them.
> >
> 
> I have no smarter ideas but I prefer 0 without any real reasons.  I
> don't get the purpose of having a SRID check constraint if the
> constraint is enforcing the unknown SRID.

Well, it's not something we have control on, it's stuff you have
in your database backup, unless you did something about it _before_
dropping it.

The only way I can think which could fix this would be changing ST_Srid
to return a SpatialRefSys object rather than an integer and make it
so an integer <= 0 casts to the _same_ SpatialRefSys object
(the "unknown srs" object). Mind you: SQL/MM does have such type...

--strk;

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