@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); }