[postgis-devel] [WKT Raster] Regular blocking restrictions

[Mateusz Loskot]

Mateusz Loskot wrote: 
> 2. All tiles must be non-overlapping.
> 
> AFAIU, it doesn't mean OGC overlapping (ST_Overlaps) but means
> overlapping of extents of all tiles:
> 
> SELECT rast && new_rast

One addition, looks like some of checks will need to be 
performed by a dedicated function, after table is filled with
tiles (blocks) and spatial index is generated.

The non-overlapping tiles test belongs to such function.

> Any ideas how to enforce restriction of all tiles appearing on regular
> block grid?

This one should be easy to express as a CHECK that performs calculations
on extent in RASTER_COLUMNS and a tile being inserted.

> 3. The top-left block must start at the top-left corner of the extent
> 
> Assuming, we don't know which is top-left tile/block, the only way to
> check this is to do full-scan to find if there is exactly one tile that
> fits this requirement.
> Also, this CHECK seems to be impossible to perform per single INSERT.
> Am I right?

The 3rd one is still unclear.
Frank, did you assume that a coverage (table) with regular_blocking
enabled does not contain "empty cells" (empty fields in table)?
IOW, all rows (tiles/blocks) of such coverage have non-NULL value in RASTER column?

Best regards,
--
Mateusz Loskot
Senior Programmer, Cadcorp
http://www.cadcorp.com