[1607] Implemented CTE to obtain entire tree hierarchy from the given…

… Group instance. Unfortunately the CTE only recurses one level when we ask Sqlalchemy to return Group instances, whereas asking for field names makes sure it recurses through the entire depth of the tree.

ckan/model/group.py

@@ -137,14 +137,15 @@ def add_child(self, object_instance):
             member = Member(group=self, table_id=getattr(object_instance,'id'), table_name=object_type_string)
             Session.add(member)
 
-    def get_children_groups(self):
-        # TODO: Investigate Using members_of_type gives an error about
-        # group appearing too many times in query
-        members = Session.query(Member).\
-               filter_by(state=vdm.sqlalchemy.State.ACTIVE).\
-               filter(Member.table_name == "group").\
-               filter(Member.group_id == self.id).all()
-        return [ Group.get( m.table_id ) for m in members ]
+    def get_children_groups(self, type='group'):
+        # Returns a list of dicts where each dict contains "id", "name", and "title"
+        # When querying with a CTE specifying a model in the query parameter causes
+        # problems as it returns only the first level deep apparently not recursing
+        # any deeper than that.  If we simplify and request only specific fields then
+        # if returns the full depth of the hierarchy.
+        results = Session.query("id","name", "title").\
+                from_statement(HIERARCHY_CTE).params(id=self.id,type=type).all()
+        return [ { "id":idf, "name": name, "title": title } for idf,name,title in results ]
 
     def active_packages(self, load_eager=True):
         query = Session.query(Package).\
@@ -251,3 +252,16 @@ def __repr__(self):
 #TODO
 MemberRevision.related_packages = lambda self: [self.continuity.package]
 
+HIERARCHY_CTE =  """
+    WITH RECURSIVE subtree(id) AS (
+        SELECT M.* FROM public.member AS M
+        WHERE M.table_name = 'group' AND M.state = 'active'
+        UNION ALL
+        SELECT M.* FROM public.member M, subtree SG
+        WHERE M.table_id = SG.group_id AND M.table_name = 'group' AND
+              M.state = 'active' )
+
+    SELECT G.* FROM subtree AS ST
+    INNER JOIN public.group G ON G.id = ST.table_id
+    WHERE group_id = :id AND G.type = :type
+"""