[postgis-devel] Re: [postgis-users] create tables smarter

[Stephen Frost]

Hi Markus,

* Markus Schaber (schabi at logix-tt.com) wrote:
> Stephen Frost <sfrost at snowman.net> wrote:
> > That allows for 4 coordinate dimensions (only 3 currently exist), 64
> > types (only 15? or so now), and over 8M SRIDs.
> 
> For the SRID, we can also add a primary key to the spatial_ref_sys
> table which is enumerated tightly, without gaps, and encode this one
> into the int. But I'd prefer having the SRID there directly.

Right, having the SRID directly encoded is best.  Where do we think the
limit on SRIDs is though?  1M?  8M?  Higher?  That's really what drives
this issue..

> > If we think that SRIDs
> > won't go over 1M, we could give it only 20 bits and keep the other 3
> > bits for 'future expansion'.
> 
> We can also use the negative bit, AFAICS.

The documentation indicates that the value must be non-negative
(negative meaning an error, I expect).

> I think this is acceptable, feel free to go ahead and present
> patches. :-)

Sounds good. :)

> I would not like to give up the possibility of "unspecified" types, for
> backwards compatibility, and for flexibility in projects which are
> not-so-strictly OpenGIS-compliant (like some we have inhouse).

Right, we would certainly want to support this, the issue I was thinking
about was that we'll have data from prior PostGIS setups that *do* have
specified types and SRIDs and whatnot, and we'll be loading them
*without* that into the new system.  We need to figure out a good way to
handle that, perhaps some script or something which goes through and
fixes it after the data is loaded.

	Thanks,

		Stephen
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