[postgis-devel] ST_Union for TopoGeometry (misnamer?)

[Sandro Santilli]

Hi all,
I've been working on a function for adding the components
of a topologically defined geometry (src TopoGeometry) to the
components of another one (tgt TopoGeometry).

In my current draft [1] this function has signature:

  toTopoGeom(src TopoGeometry, tgt TopoGeometry)

But when approaching documenting it, I figured that "toTopoGeom"
is documented to _convert_ simple geometries to TopoGeometris
while in this function there's no conversion at all.

So, the question is: would you find ST_Union [2] an appropriate
name for the function, even if it would raise an exception
when trying to union "incompatible" TopoGeometries (defined on
different topologies or different hierarchies?)

That is: is it acceptable for ST_Union(tg1, tg2) to fail
when ST_Union(tg1::geometry, tg2::geometry) would succeed ?

Your brain power is welcome :)

[1] https://gitlab.com/postgis/postgis/-/merge_requests/20
[2] https://trac.osgeo.org/postgis/ticket/4847

--strk;