One of the often overlooked features in Neo4j is the “TransactionEventHandler” capabilities… better known in the database world as “Triggers“. When a transaction occurs, we can analyze that event and decide to take some action. To accomplish this, we’ll write a “Kernel Extension” ( a little different from the Unmanaged Extensions we’ve seen on this blog ) to tie in our trigger.
In the Neo4j Property Graph model, every single Relationship must be Typed and Directed. This means they must have a specific name (FRIENDS, LIKES, FOLLOWS, etc) and have a Start Node and an End Node to show direction. What’s neat is that when you write your queries you can choose to ignore that. The following queries are all valid:
// Get all the people I follow MATCH (u1:Person)-[:FOLLOWS]->(u2:Person) WHERE u1.username = "maxdemarzi" RETURN u2.username // Get all the people that I follow or follow me MATCH (u1:Person)-[:FOLLOWS]-(u2:Person) WHERE u1.username = "maxdemarzi" RETURN u2.username // Get all the people related to me MATCH (u1:Person)--(u2:Person) WHERE u1.username = "maxdemarzi" RETURN u2.username
Neo4j 2.2 is getting released any day now, so let’s put the Release Candidate through its paces with Gatling. Once we download and start it up, you’ll notice it wants us to authenticate.
Continue reading
Max De Marzi 