Cross Product Cypher queries will not perform well

Just like SQL, if you do not properly connect the parts of your query, it will result in a cross (cartesian) product, which is seldom what you want. Take the following example:

In Cypher, what happens is that p contains all of the nodes in the graph with the :Person label, and m contains all of the nodes in the graph with the :Movie label. Returning both of these results in a combination of each node p being returned with each node m, like so:

If there are three nodes with label Person:

and three nodes with label Movie:

The result of the above Cypher would be:

Keep in mind this is a simple example, so the result set is small. With a production size graph this would be a very large and potentially memory intensive query.

In general, inadvertent cross products happen in more complex queries. They are common in queries that contain many WITH clauses and a close look at the query is needed to flush out the issue. By following general performance best practices, this can easily be avoided.

• Be as specific with your query as possible.
• Make sure to use identifiers to properly tie parts of the query together.
• Only return the data you need.
• Profile slow queries so that you can see where the time and effort is spent.