[Geopackage] Req 30: A feature table SHALL have only one geometry column.
Patrick van Dijk
patrick.van.dijk at gmail.com
Wed Oct 29 08:56:46 EDT 2014
Referring to: OGC 12-128r10 of 'Approval Date: 2014-01-19'
Any reason why this limitation exists (Req 30: A feature table SHALL have
only one geometry column.)?
Many spatial database systems like Oracle, SQL Server, Smallworld do not
have this limitation.
So why have a new standard which is limited this way?
There is an odd definition in:
CREATE TABLE gpkg_geometry_columns (
table_name TEXT NOT NULL,
column_name TEXT NOT NULL,
geometry_type_name TEXT NOT NULL,
srs_id INTEGER NOT NULL,
z TINYINT NOT NULL,
m TINYINT NOT NULL,
CONSTRAINT pk_geom_cols PRIMARY KEY (table_name, column_name),
CONSTRAINT uk_gc_table_name UNIQUE (table_name),
CONSTRAINT fk_gc_tn FOREIGN KEY (table_name)
CONSTRAINT fk_gc_srs FOREIGN KEY (srs_id)
REFERENCES gpkg_spatial_ref_sys (srs_id))
Where the primary key is defined on table_name and column_name,
but there is an additional UNIQUE CONSTRAINT on table_name.
Having just a PRIMARY KEY (table_name) would be enough, isn't it?
Then again, I can live perfectly fine without the UNIQUE (table_name)
and have multiple geometry columns per feature.
I noticed some discussions about this on
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