AbstractPlanNode childNode = recvNode.getChild(0);
assert(childNode instanceof SendPlanNode);
SendPlanNode sendNode = (SendPlanNode) childNode;
// disconnect the send and receive nodes
sendNode.clearParents();
recvNode.clearChildren();
// make a new plan fragment rooted at the send
CompiledPlan.Fragment subFrag = new CompiledPlan.Fragment();