private static void joinMapJoinPlan(Task<?> oldTask,
        GenMRProcContext opProcCtx, boolean local)
        throws SemanticException {
      TableScanOperator currTopOp = opProcCtx.getCurrTopOp();
      GenMapRedUtils.mergeInput(currTopOp, opProcCtx, oldTask, local);
    }
Merge the current task with the task for the current mapjoin. The mapjoin operator
has already been encountered.

@param op
         operator being processed
@param oldTask
         the old task for the current mapjoin
@param opProcCtx
         processing context
@param pos
         position of the parent in the stack
ql/src/java/org/apache/hadoop/hive/ql/optimizer/MapJoinFactory.java