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

[Bborie Park]

On Sat, Dec 1, 2012 at 8:03 AM, Sandro Santilli <strk at keybit.net> wrote:
> On Sat, Dec 01, 2012 at 12:20:13AM +0000, Mateusz Loskot wrote:
>
>> Blocking is a generic technique, almost equally important
>> as pyramids. We can't simply ignore it.
>
> Sorry if I ask it again (I think I didn't get an answer to that):
> is padding _necessary_ to implement "blocking" ?
>

According to my impression of the spec, yes.  Padding is in essence
rule #1 where every tile must have the same size.

http://trac.osgeo.org/postgis/wiki/WKTRaster/SpecificationWorking01

> In other words, is it really a problem if tiles exist which are
> _smaller_ than the "official" tile size ? Why do you need NODATA
> values rather than just NO values at all ?
>
> I'm probably missing something but really can't see that need.
>
> I'm trying to understand this because having no padding at all
> would solve the issue, in that the computed extent could be same
> as the original extent...
>

I'm a proponent of letting the user decide.  Just use the -r flag of
raster2pgsql to specify that tiles should be padded.  If -r flag isn't
set, don't pad.  That way the extent in raster_columns is an accurate
extent of the space covered by the set of tiles in a table.

-bborie