Optimise remove_deep, which can make removing lots of elements 100x faster in scripts.

src/ifcopenshell-python/ifcopenshell/file.py

@@ -505,6 +505,11 @@ class file:
     ) -> list[ifcopenshell.entity_instance]:
         """Return a list of entities that reference this entity
 
+        Warning: this is a slow function, especially when there is a large
+        number of inverses (such as for a shared owner history). If you are
+        only interested in the total number of inverses (typically 0, 1, or N),
+        consider using :func:`get_total_inverses`.
+
         :param inst: The entity instance to get inverse relationships
         :type inst: ifcopenshell.entity_instance
         :param allow_duplicate: Returns a `list` when True, `set` when False
@@ -530,6 +535,9 @@ class file:
     def get_total_inverses(self, inst: ifcopenshell.entity_instance) -> int:
         """Returns the number of entities that reference this entity
 
+        This is equivalent to `len(model.get_inverse(element))`, but
+        significantly faster.
+
         :param inst: The entity instance to get inverse relationships
         :type inst: ifcopenshell.entity_instance
         :returns: The total number of references

src/ifcopenshell-python/ifcopenshell/util/element.py

@@ -1315,6 +1315,8 @@ def remove_deep2(
     :type element: ifcopenshell.entity_instance
     """
     # ifc_file.batch()
+    if ifc_file.get_total_inverses(element):
+        return
     to_delete = set()
     subgraph = list(ifc_file.traverse(element, breadth_first=True))
     subgraph.extend(also_consider)
@@ -1325,7 +1327,12 @@ def remove_deep2(
         if (
             subelement.id()
             and subelement not in do_not_delete
-            and len(set(ifc_file.get_inverse(subelement)) - subgraph_set) == 0
+            and (
+                # 0 or 1 inverses means it only exists in this subgraph
+                ifc_file.get_total_inverses(subelement) < 2
+                # Alternatively, let's ensure all inverses are within the subgrpah
+                or len(set(ifc_file.get_inverse(subelement)) - subgraph_set) == 0
+            )
         ):
             to_delete.add(subelement)
             subelement_queue.extend(ifc_file.traverse(subelement, max_levels=1)[1:])