}
@Override
public void visit(LOUnion loUnion) throws FrontendException {
String scope = DEFAULT_SCOPE;
POUnion physOp = new POUnion(new OperatorKey(scope,nodeGen.getNextNodeId(scope)), loUnion.getRequestedParallelism());
physOp.addOriginalLocation(loUnion.getAlias(), loUnion.getLocation());
currentPlan.add(physOp);
physOp.setResultType(DataType.BAG);
logToPhyMap.put(loUnion, physOp);
List<Operator> ops = loUnion.getPlan().getPredecessors(loUnion);
for (Operator l : ops) {
PhysicalOperator from = logToPhyMap.get(l);