static boolean mergeInput(TableScanOperator currTopOp,
      GenMRProcContext opProcCtx, Task<?> task, boolean local)
      throws SemanticException {
    if (!opProcCtx.isSeenOp(task, currTopOp)) {
      String currAliasId = opProcCtx.getCurrAliasId();
      setTaskPlan(currAliasId, currTopOp, task, local, opProcCtx);
      return true;
    }
    return false;
  }
If currTopOp is not set for input of the task, add input for to the task
ql/src/java/org/apache/hadoop/hive/ql/optimizer/GenMapRedUtils.java