[postgis-devel] Some thoughts about PostGIS Raster I'd like to share

[dustymugs]

On 06/04/2013 10:00 AM, Jorge Arévalo wrote:
> 
> 
> El martes 4 de junio de 2013 a las 18:40, Sandro Santilli escribió:
> 
>> On Tue, Jun 04, 2013 at 06:19:46PM +0200, Jorge Arévalo wrote:
>>  
>>> For example, about scale_x: "This is only available if all tiles in the raster column have the same scale_x and this constraint is applied.". What about allowing the user to specify an strategy to calculate this, even when all tiles have different scale_x values? Same applies to scale_y. And pixel height and width. Something like the '-resolution' flag in gdalbuildvrt.
>>  
>> What do you mean by "strategy to calculate" ? Can you make an example ?
>> If all tiles have the same scale a constraint would be appropriate and
>> expose that information in the raster_table already, no ?
> 
> 
> Ok, check this http://trac.osgeo.org/gdal/browser/branches/1.10/gdal/apps/gdalbuildvrt.cpp#L1086
> 
> As resolution of all input tiles is not the same, user can provide a flag to tell gdalbuildvrt how to calculate the output resolution for the raster (average, in the example).   
> 
> In PostGIS Raster, you can have all tiles with different width, height and pixel size. Even different SRID. If you want to use them to form a dataset, you can do it in the same way VRT does. The driver can calculate this. Or the user could provide it when loading the raster data in PostGIS Raster (like gdalvrtbuild does with VRT).
> 
> I know this would mean to adapt PostGIS Raster to a particular use case. I only consider it as an option.
> 
> 

For me, what you're describing here is similar to a user wanting to use
a text column to add integer data and expect something like the
following to be fast:

mytextcolumn < 100

I just don't see something like this being appropriate for
raster_columns or embedded within a raster object. As in my analogy
above, this just seems like bad practice and violating all the best
practices when building a database model.

I could see a custom PostgreSQL background worker process that could
create a cache somewhere for consumption by clients.

-bborie