How do I find disconnected nodes on neo4j with Cypher?

Question

I am toying with neo4j and noticed that all Cypher queries need a starting point in the START clause. I was wondering how can I find all disconnected nodes using Cypher ?

thanks

Answer 1

If all your nodes are indexed (e.g. via auto-indexing) you could use an index query as a start point and then find those nodes that have no outgoing relationships.

start n=node:node_auto_index("id:*")
match n-[r?]->m
where r is null
return n

Nowadays I would rather use:

start n=node:node_auto_index("id:*")
where not (n-->m)
return n

Answer 2

I use something like this, but only when I'm using spring-data-neo4j:

    start n = node:__types__(className="com.app.entity.Model")
    // match, where...
    return n

Hope that helps!

Answer 3

With Neo4j v3.0+ I just use;

MATCH (n)
WHERE NOT (n)--()
RETURN n

(or variations thereof). The query is reasonably fast.

Answer 4

You can't. Graph global queries are not possible with todays Cypher.