@Override
public void join(Record rec1, Record rec2, Collector<Record> out) throws Exception {
// rec1 has matching start, rec2 matching end
// Therefore, rec2's end node and rec1's start node are identical
// First half of new path will be rec2, second half will be rec1
// Get from-node and to-node of new path
final StringValue fromNode = rec2.getField(0, StringValue.class);
final StringValue toNode = rec1.getField(1, StringValue.class);
// Check whether from-node = to-node to prevent circles!
if (fromNode.equals(toNode)) {
return;
}
// Create new path
outputRecord.setField(0, fromNode);
outputRecord.setField(1, toNode);
// Compute length of new path
length.setValue(
rec1.getField(2, IntValue.class).getValue()
+ rec2.getField(2, IntValue.class).getValue());
outputRecord.setField(2, length);
// compute hop count
int hops =
rec1.getField(3, IntValue.class).getValue()
+ 1
+ rec2.getField(3, IntValue.class).getValue();
hopCnt.setValue(hops);
outputRecord.setField(3, hopCnt);
// Concatenate hops lists and insert matching node
StringBuilder sb = new StringBuilder();
// first path
sb.append(rec2.getField(4, StringValue.class).getValue());
sb.append(" ");
// common node
sb.append(rec1.getField(0, StringValue.class).getValue());
// second path
sb.append(" ");
sb.append(rec1.getField(4, StringValue.class).getValue());
hopList.setValue(sb.toString().trim());
outputRecord.setField(4, hopList);
out.collect(outputRecord);
}
@Override
public void coGroup(
Iterator<Record> inputRecords, Iterator<Record> concatRecords, Collector<Record> out) {
// init minimum length and minimum path
Record pathRec = null;
StringValue path = null;
if (inputRecords.hasNext()) {
// path is in input paths
pathRec = inputRecords.next();
} else {
// path must be in concat paths
pathRec = concatRecords.next();
}
// get from node (common for all paths)
StringValue fromNode = pathRec.getField(0, StringValue.class);
// get to node (common for all paths)
StringValue toNode = pathRec.getField(1, StringValue.class);
// get length of path
minLength.setValue(pathRec.getField(2, IntValue.class).getValue());
// store path and hop count
path = new StringValue(pathRec.getField(4, StringValue.class));
shortestPaths.add(path);
hopCnts.put(path, new IntValue(pathRec.getField(3, IntValue.class).getValue()));
// find shortest path of all input paths
while (inputRecords.hasNext()) {
pathRec = inputRecords.next();
IntValue length = pathRec.getField(2, IntValue.class);
if (length.getValue() == minLength.getValue()) {
// path has also minimum length add to list
path = new StringValue(pathRec.getField(4, StringValue.class));
if (shortestPaths.add(path)) {
hopCnts.put(path, new IntValue(pathRec.getField(3, IntValue.class).getValue()));
}
} else if (length.getValue() < minLength.getValue()) {
// path has minimum length
minLength.setValue(length.getValue());
// clear lists
hopCnts.clear();
shortestPaths.clear();
// get path and add path and hop count
path = new StringValue(pathRec.getField(4, StringValue.class));
shortestPaths.add(path);
hopCnts.put(path, new IntValue(pathRec.getField(3, IntValue.class).getValue()));
}
}
// find shortest path of all input and concatenated paths
while (concatRecords.hasNext()) {
pathRec = concatRecords.next();
IntValue length = pathRec.getField(2, IntValue.class);
if (length.getValue() == minLength.getValue()) {
// path has also minimum length add to list
path = new StringValue(pathRec.getField(4, StringValue.class));
if (shortestPaths.add(path)) {
hopCnts.put(path, new IntValue(pathRec.getField(3, IntValue.class).getValue()));
}
} else if (length.getValue() < minLength.getValue()) {
// path has minimum length
minLength.setValue(length.getValue());
// clear lists
hopCnts.clear();
shortestPaths.clear();
// get path and add path and hop count
path = new StringValue(pathRec.getField(4, StringValue.class));
shortestPaths.add(path);
hopCnts.put(path, new IntValue(pathRec.getField(3, IntValue.class).getValue()));
}
}
outputRecord.setField(0, fromNode);
outputRecord.setField(1, toNode);
outputRecord.setField(2, minLength);
// emit all shortest paths
for (StringValue shortestPath : shortestPaths) {
outputRecord.setField(3, hopCnts.get(shortestPath));
outputRecord.setField(4, shortestPath);
out.collect(outputRecord);
}
hopCnts.clear();
shortestPaths.clear();
}