-This job is performed in expression.parse(). For leafs containing a path, it
-checks whether the first item of the path is a *many2one* or *one2many* field
-with the ``auto_join`` attribute set. If set, it adds a join query and recursively
-analyzes the remaining of the leaf, going back to the normal behavior when
-not reaching an ``_auto_join`` field. The sql condition created from the leaf
-will be updated to take into account the table aliases.
-
-Chaining _auto_join allows to reduce the number of queries performed, and to
-avoid having too long ``('id', 'in', ids)`` replacement leafs in domains.
-However, severe limitations exist on this feature that limits its current use as
-of version 7.0. **This feature is therefore considered as experimental, and used
+This manipulation is performed in expression.parse(). It checks leafs that
+contain a path, i.e. any domain containing a '.'. It then checks whether the
+first item of the path is a *many2one* or *one2many* field with the ``auto_join``
+attribute set. If set, it adds a join query and recursively analyzes the
+remaining of the leaf, using the same behavior. If the remaining path also holds
+a path with auto_join fields, it will add all tables and add every necessary
+join conditions.
+
+Chaining joins allows to reduce the number of queries performed, and to avoid
+having too long equivalent leaf replacement in domains. Indeed, the internal
+queries produced by this behavior can be very costly, because they were generally
+select queries without limit that could lead to huge ('id', 'in', [...])
+leafs to analyze and execute.
+
+Some limitations exist on this feature that limits its current use as of version
+7.0. **This feature is therefore considered as experimental, and used