Fix Deep Relationship filter to avoid recursion crash

Fixes #10279
This also changes filter to use shortest paths.

gramps/gen/filters/rules/person/_deeprelationshippathbetween.py

@@ -3,6 +3,7 @@
 #
 # Copyright (C) 2009 Robert Ham <rah@bash.sh>
 # Copyright (C) 2011 Adam Stein <adam@csh.rit.edu>
+# Copyright (C) 2017 Paul Culley <paulr2787@gmail.com>
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -24,6 +25,7 @@
 # Standard Python modules
 #
 #-------------------------------------------------------------------------
+from collections import deque
 from ....const import GRAMPS_LOCALE as glocale
 _ = glocale.translation.gettext
 
@@ -95,31 +97,52 @@ def get_person_family_people(db, person, person_handle):
 
     return people
 
-def find_deep_relations(db, user, person, path, seen, target_people):
-    if len(target_people) < 1:
-        return []
 
+def find_deep_relations(db, user, person, target_people):
+    """ This explores all possible paths between a person and one or more
+    targets.  The algorithm processes paths in a breadth first wave, one
+    remove at a time.  The first path that reaches a target causes the target
+    to be marked complete and the path to be stored in the return_paths set.
+    By processing in wave, the return path should be a shortest path.
+    The function stores to do data and intermediate results in an ordered dict,
+    rather than using a recursive algorithm becasue some trees have been found
+    that exceed the standard python recursive depth. """
+    return_paths = set()  # all people in paths between targets and person
     if person is None:
-        return []
+        return return_paths
+    todo = deque([person.handle])  # list of work to do, handles, add to right,
+    #                                pop from left
+    done = {}  # The key records handles already examined,
+    # the value is a handle of the previous person in the path, or None at
+    # head of path.  This forms a linked list of handles along the path.
+    done[person.handle] = None
+
+    while todo:
+        handle = todo.popleft()
 
-    handle = person.get_handle()
-    if handle in seen:
-        return []
-    seen.append(handle)
         if user:
             user.step_progress()
 
-    return_paths = []
-    person_path = path + [handle]
-
-    if handle in target_people:
-        return_paths += [person_path]
+        if handle in target_people:  # if we found a target
+            prev_hndl = handle
+            # Go through linked list and save the handles in return_paths
+            while prev_hndl:
+                return_paths.add(prev_hndl)
+                prev_hndl = done[prev_hndl]
             target_people.remove(handle)
+            if not target_people:  # Quit searching if all targets found
+                break
 
-    family_people = get_person_family_people(db, person, handle)
-    for family_person in family_people:
-        pers = db.get_person_from_handle(family_person)
-        return_paths += find_deep_relations(db, user, pers, person_path, seen, target_people)
+        person = db.get_person_from_handle(handle)
+        if person is None:
+            continue
+
+        people = get_person_family_people(db, person, handle)
+        for p_hndl in people:
+            if p_hndl in done:     # check if we have already been here
+                continue           # and ignore if we have
+            todo.append(p_hndl)    # Add to the todo list
+            done[p_hndl] = handle  # Add to the (almost) done list
 
     return return_paths
 
@@ -147,12 +170,12 @@ class DeepRelationshipPathBetween(Rule):
             user.begin_progress(_('Finding relationship paths'),
                                 _('Evaluating people'),
                                 db.get_number_of_people())
-        paths = find_deep_relations(db, user, root_person, [], [], target_people)
+        self.__matches = find_deep_relations(db, user, root_person, target_people)
         if user:
             user.end_progress()
 
-        self.__matches = set()
-        list(map(self.__matches.update, paths))
+#         self.__matches = set()
+#         list(map(self.__matches.update, paths))
 
     def reset(self):
         self.__matches = set()