[Geopackage] gpkg_contents when type is not 'feature' or 'tiles'

Pepijn Van Eeckhoudt pepijn.vaneeckhoudt at luciad.com
Fri Nov 14 11:32:02 EST 2014


I’m wondering if the confusion is caused by the usage of ‘applying’ an extension. 2.5.2.1.1 states
> The gpkg_extensions table or updateable view in a GeoPackage is used to indicate that a particular extension applies to a GeoPackage, a table in a GeoPackage or a column of a table in a GeoPackage

Perhaps that would be better as:
> The gpkg_extensions table in a GeoPackage describes which tables and columns of tables in a GeoPackage make use of features described in GeoPackage extensions.

Does that make it clearer that the intended meaning of a row in gpkg_extensions is one of the following?
table_name null, column_name null, extension_name E
extension E is used by the entire geopackage. If you don’t support this extension you probably can’t do anything useful with any data in this geopackage
table_name T, column_name null, extension_name E
extension E is used by table E. If you don’t support this extension you probably can’t do anything useful with table T
table_name T, column_name C, extension_name E
extension E is used by column C of table E. If you don’t support this extension you probably can’t interpret that one column correctly

The problem with using 1. for aspatial tables is that it basically says all tables (even tiles and features tables) are making use of the gdal_aspatial extension. 

Pepijn
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