Best way to delete all nodes and relationships in Cypher

Question

What is the best way to cleanup the graph from all nodes and relationships via Cypher?

At http://neo4j.com/docs/stable/query-delete.html#delete-delete-a-node-and-connected-relationships the example

MATCH (n)
OPTIONAL MATCH (n)-[r]-()
DELETE n,r

has the note:

This query isn’t for deleting large amounts of data

So, is the following better?

MATCH ()-[r]-() DELETE r

and

MATCH (n) DELETE n

Or is there another way that is better for large graphs?

Answer 1

As you've mentioned the most easy way is to stop Neo4j, drop the data/graph.db folder and restart it.

Deleting a large graph via Cypher will be always slower but still doable if you use a proper transaction size to prevent memory issues (remember transaction are built up in memory first before they get committed). Typically 50-100k atomic operations is a good idea. You can add a limit to your deletion statement to control tx sizes and report back how many nodes have been deleted. Rerun this statement until a value of 0 is returned back:

MATCH (n)
OPTIONAL MATCH (n)-[r]-()
WITH n,r LIMIT 50000
DELETE n,r
RETURN count(n) as deletedNodesCount

Answer 2

According to the official document here:

MATCH (n)
DETACH DELETE n

but it also said This query isn’t for deleting large amounts of data. so it's better use with limit.

match (n)  
with n limit 10000  
DETACH DELETE n;  

Answer 3

Wrote this little script, added it in my NEO/bin folder.

Tested on v3.0.6 community

#!/bin/sh
echo Stopping neo4j
./neo4j stop
echo Erasing ALL data
rm -rf ../data/databases/graph.db
./neo4j start
echo Done

I use it when my LOAD CSV imports are crappy.

Hope it helps