Hi Neo4j users and developers, I've been playing with Neo4j a bit lately; I'm using data from the GHTorrent project (http://ghtorrent.org) to answer some questions about the relationships between GitHub users and projects. The first thing I did was to import all users as nodes with the type "User", and the following relationship as nodes with type "Follower"- I figured I'd import the data before establishing the relationships between them. Followers have user_id and follower_id; I created indices on each of these, as well as on User.id. I tried to make a FOLLOWS relationship like so:
MATCH (f:Follower),(followee:User),(follower:User) WHERE f.user_id = followee.id AND f.follower_id = follower.id CREATE (follower)-[:FOLLOWS]->(followee) For a sense of the size of the data involved, there are about 3.7M Users in the dataset, and about 4.8M following relationships. I ran the above statement, and after a while, I tried an EXPLAIN on it. EXPLAIN explained to me that it was taking the cartesian product of the two users "tables", and then whittling them down. The cartesian product was a gigantic number, and I'm doubting it would ever finish. Is there a better way to go about creating the relationship? I then had the idea to not create a Follower type, but just create the relationship via the followers CSV load. To do this, I tried removing all follower nodes: MATCH (n:Follower) DELETE n This also took some time, until the browser page pointed at Neo4j reported that Neo4j was no longer responding. I was unable to connect via neo4j-shell as well (timeout), and the server didn't respond to SIGTERM or SIGINT, so I had to give it a SIGKILL. Before I killed it, I observed a lot of CPU load on part of the java process. Is there something I'm missing about why Neo4j would freeze up like this? I'm really a novice at Neo4j, and I am probably improperly applying a lot of knowledge from the RDBMS world. Does anyone have any pointers or advice for what I'm doing? I'm running Neo4j 2.2.0 on Arch Linux. Please let me know if you need more information from me. Thanks, Rob -- You received this message because you are subscribed to the Google Groups "Neo4j" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
