@Override
public SubPlanBuilder visitTopN(TopNNode node, Void context)
{
SubPlanBuilder current = node.getSource().accept(this, context);
current.setRoot(new TopNNode(node.getId(), current.getRoot(), node.getCount(), node.getOrderBy(), node.getOrderings(), false));
if (current.isDistributed()) {
current.setRoot(new SinkNode(idAllocator.getNextId(), current.getRoot(), current.getRoot().getOutputSymbols()));
// create merge plan fragment
PlanNode source = new ExchangeNode(idAllocator.getNextId(), current.getId(), current.getRoot().getOutputSymbols());
TopNNode merge = new TopNNode(idAllocator.getNextId(), source, node.getCount(), node.getOrderBy(), node.getOrderings(), true);
current = createSingleNodePlan(merge)
.addChild(current.build());
}
return current;