[postgis-devel] Xing Lin's SoC project (raster support)

Paul Ramsey pramsey at refractions.net
Wed Jul 11 13:01:41 PDT 2007

More specifically, there is a lot of talk about "user defined types" in 
this document, but the model does not really require any -- the whole 
thing can be done with relations.  Doing it as UDT's requires lots of 
book-keeping code for accessors to the properties of the types, doing it 
as relations does not.

The same thing could be said about geometry, of course, but the 
difference is that geometry objects have a unitary structure that only 
makes sense in aggregate, so breaking them up is wasteful -- you have to 
put them back together again before they are useful.

This is less true of these georasters, and in fact they will be somewhat 
broken up anyways, into bands, for example.  Why not start this process 
by building the whole thing as a relational model and then see what 
doesn't work well and needs a UDT for efficiency?


Paul Ramsey wrote:
> I'm a little worried at the quantity of this document that is copied 
> verbatim from the Oracle Georaster documentation.  I mean, are we just 
> cribbing their whole design directly?  The Oracle model is pretty, but 
> it breaks up the rasters into an internal relational model, which pretty 
> much requires some sort of toolset for people to load/unload data.
> Second, the documentation stops with the model, it provides no 
> functions, or even hint of what functions will be done first. Providing 
> objects and no functions, or no data loader, is going to be a pure Waste 
> of Time. I know he's not going to have time to copy the complete set of 
> Georaster functions from Oracle, so an idea of what functions he plans 
> to do first is pretty important.
> PostGIS 0.1 had the types, it had input/output methods, and it had index 
> bindings.  If this implementation does not have a way of getting data in 
> and out, it's not going to be worth the time putting it together.
> P.
> Tim Keitt wrote:
>> I'm attaching a proposal to add raster support to postgis. This is
>> Xing Lin's SoC project. I'm hoping to get feedback on the spec and
>> ideas for additions, modifications. Implementation is underway, but
>> its not too late to make changes if people see significant problems or
>> have suggestions.
>> Cheers,
>> Tim
>> ------------------------------------------------------------------------
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   Paul Ramsey
   Refractions Research
   pramsey at refractions.net
   Phone: 250-383-3022
   Cell: 250-885-0632

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