Function to drop TopoGeometry objects not found in their layers

[strk]

It happens that TopoGeometry objects exist in the "relation" table but are not reachable from their layer tables anymore. A simple DELETE or UPDATE on the layer table could be the cause of this.

It would be useful to have a function to drop all such "orphaned" objects.

Not sure how to threat objects associated with non deployed or otherwise invalid layers (layers for which the associated schema.table.column doesn't exist).

[robe]

strk -- do you consider this related to my complaint in #1186

[strk]

Yeah, sound like we can close #1186 and point here

[strk]

I've code locally for this, btw. Only I can't decide if the function should return something, and if so, what. I've been thinking a list of distinct layer_id,topogeo_id could be nice but would require some overhead.