public void constructList() throws Exception {
//
// Create a counter for each node based on the # of children that it has
// If any node has no children, put it in the execute list
//
List<AbstractPlanNode> execute_list =
Collections.synchronizedList(new ArrayList<AbstractPlanNode>());
Map<AbstractPlanNode, Integer> child_cnts = new HashMap<AbstractPlanNode, Integer>();
for (AbstractPlanNode node : m_planNodes) {
int num_of_children = node.getChildCount();
if (num_of_children == 0) {
execute_list.add(node);
} else {
child_cnts.put(node, num_of_children);
}
}
//
// Now run through a simulation
// Doing it this way maintains the nuances of the parent-child relationships
//
m_list.clear();
while (!execute_list.isEmpty()) {
AbstractPlanNode node = execute_list.remove(0);
//
// Add the node to our execution list
//
m_list.add(node);
//
// Then update all of this node's parents and reduce their wait counter by 1
// If the counter is at zero, then we'll add it to end of our list
//
for (int i = 0; i < node.getParentCount(); i++) {
AbstractPlanNode parent = node.getParent(i);
int remaining = child_cnts.get(parent) - 1;
child_cnts.put(parent, remaining);
if (remaining == 0) {
execute_list.add(parent);
}
}
}
//
// Important! Make sure that our list has the same number of entries in our tree
//
if (m_list.size() != m_planNodes.size()) {
throw new Exception(
"ERROR: The execution list has '"
+ m_list.size()
+ "' PlanNodes but our original tree has '"
+ m_planNodes.size()
+ "' PlanNode entries");
}
return;
}
