[postgis-devel] [PostGIS] #2122: [raster] Real extent feature lost after metadata as views

[Mateusz Loskot]

On 3 December 2012 16:05, Sandro Santilli <strk at keybit.net> wrote:
> On Mon, Dec 03, 2012 at 03:13:00PM +0000, Mateusz Loskot wrote:
>> On 1 December 2012 16:03, Sandro Santilli <strk at keybit.net> wrote:
>>
>> Despite technically possible tohandle, it would complicate things though.
>> Is actual blocksize < max_blocksize_x|y allowed only along the right and
>> the bottom edge?
>
> No, I think it should be allowed everywhere

Then, we no longer discuss blocking in a regular grid.

>> GDAL requires the same blocksize for all tiles in a GDALRasterBand
>>
>> http://www.gdal.org/classGDALRasterBand.html#af2ee6fa0f675d7d52bc19f826d161ad6
>>
>> I doubt it's possible for GDAL to cope with mixed blocksize.
>
> I guess GDAL could just ensure the same blocksize when reading the rasters.
> There's an ST_Resize function IIRC.

This is optimisation feature, cache feature, predictable memory constraint, etc.

>> In GDAL driver for PostGIS Raster, there is currently an explicit check
>> that the "blocks" all have the same size, to imply regular blocking:
>>
>> http://trac.osgeo.org/gdal/browser/trunk/gdal/frmts/postgisraster/postgisrasterdataset.cpp#L561
>
> I think GDAL should use other means to tell if a raster table
> is "regularly blocked" or not. For a start there's metadata
> to lookup, and if that's too limiting the user could specify
> a tile size and the driver could check for NO tile to be bigger
> in any direction.

The original issue of spatial extent remains unresolved.

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net