code: @SuppressWarnings({ "unchecked" })
      public static SelectResults<Object> executeOnBuckets(String queryString, Region region, Set<Object> keys)
  	    throws QueryException {
  	return executeOnBuckets(queryString, null, region, keys);
      }
docs: Executes a particular query on specified region using a set of keys that represents buckets. The set of buckets is
  determined by keys of entries that are stored in such buckets: - real and fake keys can be used (such key should
  have the same routing object as bucket's keys have); - it will be enough to specify one key for each bucket. Work
  of this method is based on execution of function.
  
  @see BucketOrientedQueryFunction
  @param queryString OQL query string.
  @param region Partitioned region on which query will be executed.
  @param keys Set of keys that specify buckets.
  @return Query results as instance of {@link SelectResults}.
  @throws QueryException When in case of query execution failure.