Applying Predicates and Partition Pruning to MERGE Target Tables

Just a quick pointer to an answer on the Oracle Forum:  http://forums.oracle.com/forums/thread.jspa?messageID=3912341#3912341

If you are merging into a data warehouse fact table (not so likely) or a large aggregation of a fact table (more likely) then you can improve efficiency by adding a transitive predicate into the USING clause to promote partition pruning on the target table.

Unless you are using Partition Change Tracking I think it is very unlikely that the MERGE inherent to a materialized view refresh is going to partition prune on the target table.