Question

This seems like a very strange problem. I’m stress testing my neo4j graph database, and so one of my tests requires creating a lot of users (in this specific test, 1000). So the code for that is as follows,

// Creates a n users and measures the time taken to add another
            n = 1000;
            tx = graphDb.beginTx();
            try {
                for(int i = 0; i < n; i++){
                    dataService.createUser(BigInteger.valueOf(i));
                }

                start = System.nanoTime();
                dataService.createUser(BigInteger.valueOf(n));
                end = System.nanoTime();

                time = end - start;

                System.out.println("The time taken for createUser with " + n + " users is " + time +" nanoseconds.");

                tx.success();
            }
            finally
            {
                tx.finish();
            }

And the code for dataService.createUser() is,

public User createUser(BigInteger identifier) throws ExistsException {
        // Verify that user doesn't already exist.
        if (this.nodeIndex.get(UserWrapper.KEY_IDENTIFIER, identifier)
                .getSingle() != null) {
            throw new ExistsException("User with identifier '"
                    + identifier.toString() + "' already exists.");
        }

        // Create new user.
        final Node userNode = graphDb.createNode();
        final User user = new UserWrapper(userNode);
        user.setIdentifier(identifier);

        userParent.getNode().createRelationshipTo(userNode, NodeRelationships.PARENT);

        return user;
    }

Now I need to call dataService.getUser() after I’ve made these Users. The code for getUser() is as follows,

public User getUser(BigInteger identifier) throws DoesNotExistException {
        // Search for the user.
        Node userNode = this.nodeIndex.get(UserWrapper.KEY_IDENTIFIER,
                identifier).getSingle();
        // Return the wrapped user, if found.
        if (userNode != null) {
            return new UserWrapper(userNode);
        } else {
            throw new DoesNotExistException("User with identifier '"
                    + identifier.toString() + "' was not found.");
        }
    }

So everything is going fine until I create the 129th user. I’m following along in the debugger and watching the value of dataService.getUser(BigInteger.valueOf(1)) which is the second node, dataService.getUser(BigInteger.valueOf(127)) which is the 128th node, and dataService.getUser(BigInteger.valueOf(i-1)) which is the last node created. And the debugger is telling me that after node 128 is created, node 129 and above aren’t created because getUser() throws a DoesNotExistException for those nodes, but still gives values for node 2 and node 128.

The user id I’m passing to createUser() is autoindexed.

Any idea why it isn’t making more nodes (or not indexing these nodes)?

Answer 1

It sounds suspiciously like a byte value conversion which flips around at 128. Could you make sure there isn’t anything like that going on in your code?