private Operator genNotNullFilterForJoinSourcePlan(QB qb, Operator input,
                                                        QBJoinTree joinTree, ExprNodeDesc[] joinKeys) throws SemanticException {
    return genNotNullFilterForJoinSourcePlan(qb, input, joinTree, joinKeys, false);
  }
create a filter plan. The condition and the inputs are specified.

@param qb
         current query block
@param condn
         The condition to be resolved
@param input
         the input operator
ql/src/java/org/apache/hadoop/hive/ql/parse/SemanticAnalyzer.java