// Find re-aggregation node.
assertTrue(p instanceof ReceivePlanNode);
assertTrue(p.getParent(0) instanceof HashAggregatePlanNode);
HashAggregatePlanNode reAggNode = (HashAggregatePlanNode) p.getParent(0);
String reAggNodeStr = reAggNode.toExplainPlanString().toLowerCase();
// Find scan node.
p = pns.get(1);
assert (p.getScanNodeList().size() == 1);
p = p.getScanNodeList().get(0);