TopoElementArray cannot be null

[strk]

Trying to GetTopoElementArray for an empty TopoGeometry fails due to NULL not passing the TopoElementArray domain constraint:

t=# select null::topoelementarray;
ERROR:  value for domain topoelementarray violates check constraint "dimensions"

I think the check should allow for null…

[strk]

Now this is funny, I can create a NULL TopoElementArray like this:

SELECT topology.TopoElementArray_agg(e)::TopoElementArray IS NULL from (        
  SELECT '{1,1}'::TopoElement WHERE false                                       
) as foo(e);

Now I wonder why the "dimensions" constraint only kicks in with a literal ! This is PostgreSQL 9.3.6.

The domain definition is here: ​https://trac.osgeo.org/postgis/browser/tags/2.2.0/topology/topology.sql.in#L384

[Algunenano]

Moving to a non EOL release.

[robe]

Still doesn't work on PostgreSQL 13.

Is there a reason we can't just change the constraint to:

ALTER DOMAIN topology.topoelementarray DROP CONSTRAINT  dimensions;
ALTER DOMAIN topology.topoelementarray
    ADD CONSTRAINT dimensions CHECK ( array_upper(VALUE, 2) = 2 AND array_upper(VALUE, 3) IS NULL);
	

Then the NULL thing wouldn't violate because NULL is special. Then the below works.

SELECT null::topoelementarray;

[robe]

strk said on IRC okay to make the change, but I feel it's not kosher to do in a micro release so pushing to 3.1.0.

[Regina Obe <lr@…>]

In 5829c16/git:

Change TopologyElementArray constraint to not exclude null and minor cleanup on news. Closes #3372 for PostGIS 3.1