Can anyone to give me a sample script that a load has precessors?

[Zhang, Liyun]

Hi all
I found that:
org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MRCompiler#compile
Line 384~433 this code is for dealing with the situation where a load has 
predecessors.  Can anyone to give me a sample script that a load has precessors?
  else if (predecessors != null && predecessors.size() > 0) {
            // When processing an entire script (multiquery), we can
            // get into a situation where a load has
            // predecessors. This means that it depends on some store
            // earlier in the plan. We need to take that dependency
            // and connect the respective MR operators, while at the
            // same time removing the connection between the Physical
            // operators. That way the jobs will run in the right
            // order.
            if (op instanceof POLoad) {

                if (predecessors.size() != 1) {
                    int errCode = 2125;
                    String msg = "Expected at most one predecessor of load. Got 
"+predecessors.size();
                    throw new PlanException(msg, errCode, PigException.BUG);
                }

                PhysicalOperator p = predecessors.get(0);
                MapReduceOper oper = null;
                if(p instanceof POStore || p instanceof PONative){
                    oper = phyToMROpMap.get(p);
                }else{
                    int errCode = 2126;
                    String msg = "Predecessor of load should be a store or 
mapreduce operator. Got "+p.getClass();
                    throw new PlanException(msg, errCode, PigException.BUG);
                }

                // Need new operator
                curMROp = getMROp();
                curMROp.mapPlan.add(op);
                MRPlan.add(curMROp);

                plan.disconnect(op, p);
                MRPlan.connect(oper, curMROp);
                phyToMROpMap.put(op, curMROp);
                return;
            }

            Collections.sort(predecessors);
            compiledInputs = new MapReduceOper[predecessors.size()];
            int i = -1;
            for (PhysicalOperator pred : predecessors) {
                if(pred instanceof POSplit && 
splitsSeen.containsKey(pred.getOperatorKey())){
                    compiledInputs[++i] = 
startNew(((POSplit)pred).getSplitStore(), 
splitsSeen.get(pred.getOperatorKey()));
                    continue;
                }
                compile(pred);
                compiledInputs[++i] = curMROp;
            }
        } else {




Best Regards
Zhang,Liyun