The main difference between graph databases and triple stores is how they model the graph. In a triple store (or quad store), the data tends to be very atomic. What I mean is that the “nodes” in the graph tend to be primitive data types like string, integer, date, etc. Relationships link primitives together, and … Read more
What you are doing will not work for root user. Maybe you are running your services as root and hence you don’t get to see the change. To increase the ulimit for root user you should replace the * by root. * does not apply for root user. Rest is the same as you did. … Read more
As of 2.3.0 and up to 3.3.0 MATCH (n) DETACH DELETE n Docs Pre 2.3.0 MATCH (n) OPTIONAL MATCH (n)-[r]-() DELETE n,r Docs
Update 01/10/2013: Came across this in the Neo4j 2.0 reference: Try not to use optional relationships. Above all, don’t use them like this: MATCH a-[r?:LOVES]->() WHERE r IS NULL where you just make sure that they don’t exist. Instead do this like so: MATCH a WHERE NOT (a)-[:LOVES]->() Using cypher for checking if relationship doesn’t … Read more
MATCH (s) WHERE ID(s) = 65110 RETURN s The ID function gets you the id of a node or relationship. This is different from any property called id or ID that you create.
Shut down your Neo4j server, do a rm -rf data/graph.db and start up the server again. This procedure completely wipes your data, so handle with care.
You can just remove the entire graph directory with rm -rf, because Neo4j is not storing anything outside that: rm -rf data/* Also, you can of course iterate through all nodes and delete their relationships and the nodes themselves, but that might be too costly just for testing …
For general querying, Cypher is enough and is probably faster. The advantage of Gremlin over Cypher is when you get into high level traversing. In Gremlin, you can better define the exact traversal pattern (or your own algorithms) whereas in Cypher the engine tries to find the best traversing solution itself. I personally use Cypher … Read more
I used a graph database in a previous job. We weren’t using neo4j, it was an in-house thing built on top of Berkeley DB, but it was similar. It was used in production (it still is). The reason we used a graph database was that the data being stored by the system and the operations … Read more