explain and query plan cache

Author: kay-kim

source/core/query-plans.txt

@@ -93,8 +93,10 @@ plan and re-evaluates after any of the following events:
 
 - The :program:`mongod` process restarts.
 
-- You run :method:`db.collection.explain()` or
-  :method:`cursor.explain()`.
+.. versionchanged:: 2.6
+
+   ``explain()`` operations no longer read from or write to the query
+   planner cache.
 
 Cached Query Plan Interface
 ---------------------------