Make SceneGraph.ForEachSOG() execute once for each SOG, not once for each prim (e.g. a SOG with 3 prims would have the action executed three times).

To do this, a new SceneObjectGroupsByFullID index in SceneGraph which just index's prims by their root part UUID, in order to avoid the inefficiency of filtering existing lists.
Existing callers to SceneGraph.ForEachSOG() did not fail due to the multiple per SOG action executions - they were probably just much less efficient.
Code suggests that no callers expected ForEachSOG() to execute actions on sog multiple times

OpenSim/Region/Framework/Scenes/SceneGraph.cs

@@ -88,9 +88,21 @@ namespace OpenSim.Region.Framework.Scenes
         protected internal object m_syncRoot = new object();
 
         protected internal PhysicsScene _PhyScene;
-
+        
-        protected internal Dictionary<uint, SceneObjectGroup> SceneObjectGroupsByLocalPartID = new Dictionary<uint, SceneObjectGroup>();
+        /// <summary>
+        /// Index the SceneObjectGroup for each part by the root part's UUID.
+        /// </summary>
+        protected internal Dictionary<UUID, SceneObjectGroup> SceneObjectGroupsByFullID = new Dictionary<UUID, SceneObjectGroup>();
+        
+        /// <summary>
+        /// Index the SceneObjectGroup for each part by that part's UUID.
+        /// </summary>
         protected internal Dictionary<UUID, SceneObjectGroup> SceneObjectGroupsByFullPartID = new Dictionary<UUID, SceneObjectGroup>();
+        
+        /// <summary>
+        /// Index the SceneObjectGroup for each part by that part's local ID.
+        /// </summary>
+        protected internal Dictionary<uint, SceneObjectGroup> SceneObjectGroupsByLocalPartID = new Dictionary<uint, SceneObjectGroup>();        
 
         private Object m_updateLock = new Object();
 
@@ -131,6 +143,8 @@ namespace OpenSim.Region.Framework.Scenes
                 m_scenePresenceArray = newlist;
             }
 
+            lock (SceneObjectGroupsByFullID)
+                SceneObjectGroupsByFullID.Clear();
             lock (SceneObjectGroupsByFullPartID)
                 SceneObjectGroupsByFullPartID.Clear();
             lock (SceneObjectGroupsByLocalPartID)
@@ -384,6 +398,9 @@ namespace OpenSim.Region.Framework.Scenes
             if (OnObjectCreate != null)
                 OnObjectCreate(sceneObject);
 
+            lock (SceneObjectGroupsByFullID)
+                SceneObjectGroupsByFullID[sceneObject.UUID] = sceneObject;
+            
             lock (SceneObjectGroupsByFullPartID)
             {
                 SceneObjectGroupsByFullPartID[sceneObject.UUID] = sceneObject;
@@ -426,6 +443,9 @@ namespace OpenSim.Region.Framework.Scenes
 
             if (OnObjectRemove != null)
                 OnObjectRemove(Entities[uuid]);
+            
+            lock (SceneObjectGroupsByFullID)
+                SceneObjectGroupsByFullID.Remove(grp.UUID);
 
             lock (SceneObjectGroupsByFullPartID)
             {
@@ -1064,12 +1084,13 @@ namespace OpenSim.Region.Framework.Scenes
         }
 
         /// <summary>
-        /// Performs action on all scene object groups.
+        /// Performs action once on all scene object groups.
         /// </summary>
         /// <param name="action"></param>
         protected internal void ForEachSOG(Action<SceneObjectGroup> action)
         {
-            List<SceneObjectGroup> objlist = new List<SceneObjectGroup>(SceneObjectGroupsByFullPartID.Values);
+            // FIXME: Need to lock here, really.
+            List<SceneObjectGroup> objlist = new List<SceneObjectGroup>(SceneObjectGroupsByFullID.Values);
             foreach (SceneObjectGroup obj in objlist)
             {
                 try
@@ -1084,7 +1105,6 @@ namespace OpenSim.Region.Framework.Scenes
                 }
             }
         }
-
         
         /// <summary>
         /// Performs action on all scene presences. This can ultimately run the actions in parallel but