Operating on Vertices - Aster Execution Engine

   private String path = "";

This variable will be referenced by the operateOnVertex() and emitFinalRows() methods.

int target_vertex_id;
VertexKey target_vertex_key;
VertexKey vertex_key = vertexState.getVertex().getVertexKey();
int vertex_id = vertex_key.getIntAt(0);
EdgeIterator edgeIterator = vertexState.getEdgeIterator();
System.out.println("++++++++++++++++++++++++++++++++++++++");
System.out.println("This is iteration # " + globals.getIteration());
System.out.println("Operating on vertex " + vertex_id);
System.out.println();	
if(vertex_id == sourceArgument){
	System.out.println("Operating on the source node ("+vertex_id+")...");	
	while (edgeIterator.advanceToNextEdge()){
		target_vertex_key = edgeIterator.getEdge().getTargetVertexKey();
		target_vertex_id = target_vertex_key.getIntAt(0);
		System.out.println("There is an edge to vertex: "+target_vertex_id);	
		// Add vertex ID to message.
		System.out.println("Adding to message");	
		outputMessages.addInt(vertex_id);
		outputMessages.addString(String.valueOf(vertex_id));
		// Send message to target vertex.
		System.out.println("Sending message...");	
		outputMessages.emitVertexMessage(target_vertex_key);
	}
	System.out.println();	
	vertexState.localHalt();
} else if(vertex_id == destinationArgument){
		System.out.println("Operating on the destination node");
		// If a message is received with containing the ID of the source node, 
		// issue a global halt.
	if (inputMessages.advanceToNextMessage()){
		if (inputMessages.getIntAt(0)== sourceArgument){
			System.out.println("The destination vertex is reachable from vertex " +
				sourceArgument);
			path = inputMessages.getStringAt(1)+
				" > "+String.valueOf(destinationArgument);
			globals.globalHalt();
		}
	}
	System.out.println();
}
else {
	if (inputMessages.advanceToNextMessage()){
		if (inputMessages.getIntAt(0)== sourceArgument){
			System.out.println("Vertex (" + vertex_id + 
			") is reachable from vertex " + inputMessages.getIntAt(0));
			// Add vertex ID of source vertex to message.
			while (edgeIterator.advanceToNextEdge()){
				target_vertex_key = edgeIterator.getEdge().getTargetVertexKey();
				target_vertex_id = target_vertex_key.getIntAt(0);
				System.out.println("There is an edge to vertex: "+target_vertex_id);	
				// Add vertex ID of source vertex to message.
				outputMessages.addInt(sourceArgument);
				outputMessages.addString(inputMessages.getStringAt(1)+
				                    " > "+String.valueOf(vertex_id));
				// Send message to target vertex.
				outputMessages.emitVertexMessage(target_vertex_key);
			}
			vertexState.localHalt();	
		}					
	}
}

if (globals.isGlobalHalt() &&(vertexState.getVertex().getVertexKey().getIntAt(0)==
				destinationArgument)){
	// This means that the destination vertex is reachable from the source vertex.
	// Emit the path leading to the destination vertex.
	emitter.addString(path);
	emitter.emitRow();
		}

select * from HelloWorld(
  on vertices as vtable partition by vid
  on edges as etable partition by src
  source(1) destination(4)
) order by 1;
The output looks like this:
path          
-----------------------
1 > 2 > 7 > 6 > 3 > 4
(1 row)

For more examples, see SQL-GR™ Function Examples_stub.