Delete all nodes and relationships in neo4j 1.8 - neo4j

I know this question is asked by many people already
for my research, here's some questions asked before
How to delete all relationships in neo4j graph?
https://groups.google.com/forum/#!topic/neo4j/lgIaESPgUgE
But after all, still can't solve our problems,
we just want to delete "ALL" nodes and "ALL" relationships
suppose delete "ALL" can see there are left 0 nodes 0 properties and 0 relationships
This is the screenshot i took after executing the delete "ALL" suggested by forum
My question still the same, how do delete all nodes and all relationships in neo4j

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

you are probably doing it correct, only the dashboard shows just the higher ID taken, and thus the number of "active" nodes, relationships, although there are none. it is just informative.
to be sure you have an empty graph, run this command:
START n=node(*) return count(n);
START r=rel(*) return count(r);
if both give you 0, your deletion was succesfull.

for a big database you should either remove the database from the disk (after you stop the engine first I guess) or use in Cypher something like:
MATCH (n)
OPTIONAL MATCH (n)-[r]-()
WITH n,r LIMIT 50000
DELETE n,r
RETURN count(n) as deletedNodesCount
see https://zoomicon.wordpress.com/2015/04/18/howto-delete-all-nodes-and-relationships-from-neo4j-graph-database/ for some more info I've gathered on this from various answers

Neo4j cannot delete nodes that have a relation. You have to delete the relations before you can delete the nodes.
But, it is simple way to delete "ALL" nodes and "ALL" relationships with a simple chyper.
This is the code:
MATCH (n) DETACH DELETE n
DETACH DELETE will remove all of the nodes and relations by Match

if the name of node is for example : abcd then below query will work :
MATCH (n:abcd)
DETACH DELETE n
This will only delete the node with label "abcd" and all its relation-ships.

Probably you will want to delete Constraints and Indexes

It will do the trick..
Match (n)-[r]-()
Delete n,r;

Related

Neo4j Delete All Nodes and Relationships

I want to delete all nodes and relationships.
I run MATCH ()-[r]-() DELETE r to delete all the relationships.
Then, I run MATCH (n) DELETE n to delete all the nodes. It does delete all the nodes, but the problem is that it also gives me this error:
Neo.DatabaseError.Transaction.TransactionCommitFailed
Unable to complete transaction.
How do I delete all nodes and relationships with getting this error?
To delete all nodes and all relationships, I do DETACH DELETE
Reference:
https://neo4j.com/docs/cypher-manual/current/clauses/delete/#delete-delete-all-nodes-and-relationships
MATCH (n)
DETACH DELETE n;
If nothing works, then rename (or remove) your neo4j data folder and restart your server.
<HOME_NEO4j>/data/data/transactions/neo4j
It looks like your database is hitting an OOM Exception.
As stated in Large Delete Transaction Best Practices in Neo4j
If you need to delete some large number of objects from the graph, one needs to be mindful of the not building up such a large single transaction such that a Java OUT OF HEAP Error will be encountered.
Delete all constraints and indexes
CALL apoc.schema.assert({},{},true);
Batch delete with CALL {} IN TRANSACTIONS syntax or apoc.periodic.iterate:
MATCH (n:Foo) where n.foo='bar'
CALL { WITH n
DETACH DELETE n
} IN TRANSACTIONS OF 10000 ROWS;
OR
CALL apoc.periodic.iterate(
"MATCH (n) RETURN n",
"DETACH DELETE n",
{batchSize:10000, parallel:false})

Unable to load NODE with id

I recently upgraded my Neo4j database to v. 3 (3.0.6). Since then I am having trouble when trying to delete nodes with Cypher. This is a new problem since the upgrade. They Cypher query is:
MATCH (p) WHERE id(p) = 83624
OPTIONAL MATCH (p)-[r]-(n)
OPTIONAL MATCH (p)-[r2]-(n2)
WHERE NOT ('Entity' in labels(n2))
DELETE r, r2, p, n2
This now results in the error Unable to load NODE with id 83624
The exact query with RETURN instead of DELETE returns the node. I've also tried swapping out DELETE with DETACH DELETE of the nodes, but that gives me the same error.
It looks like this question has been asked before but without a solution. Any idea what is causing this error?
I'm a little confused by this query. Both of your optional matches are identical, in that they will match to any relationship to any node connected to p.
Let me make sure I understand what you're trying to do: Find a node by ID, then delete that node along with any connected node that is not an Entity (as well as the relationships connecting them). Is that right?
If so, this query might work better:
MATCH (p) WHERE id(p) = 83624
OPTIONAL MATCH (p)--(n)
WHERE NOT n:Entity
DETACH DELETE n
DETACH DELETE p
Detaching a node deletes all relationships connected to that node, and you can only delete a node that has zero relationships.
Also, just to note, it's not a good idea to use the internal ids for uniquely identifying nodes. It's recommended to use your own unique IDs instead, and create unique constraints on that property for that label.

What's the Cypher script to delete a node by ID?

In SQL:
Delete From Person Where ID = 1;
In Cypher, what's the script to delete a node by ID?
(Edited: ID = Neo4j's internal Node ID)
Assuming you're referring to Neo4j's internal node id:
MATCH (p:Person) where ID(p)=1
OPTIONAL MATCH (p)-[r]-() //drops p's relations
DELETE r,p
If you're referring to your own property 'id' on the node:
MATCH (p:Person {id:1})
OPTIONAL MATCH (p)-[r]-() //drops p's relations
DELETE r,p
The cleanest sweep for a node with id "x" is
MATCH (n) where id(n) = x
DETACH DELETE n
https://neo4j.com/docs/cypher-manual/current/clauses/delete/#delete-delete-a-node-with-all-its-relationships
https://neo4j.com/docs/cypher-manual/current/functions/scalar/#functions-id
Old question and answered, but to delete node when it has relationships, use DETACH
MATCH (n) where ID(n)=<your_id>
DETACH DELETE n
or otherwise you get this:
Neo.ClientError.Schema.ConstraintValidationFailed: Cannot delete node<21>, because it still has relationships. To delete this node, you must first delete its relationships.
It's like SQL's CASCADE
When the node is a orphan.
Start n=node(1)
Delete n;
Following the link provided by #saad-khan, here's an example for getting the nodes and relationships ids.
The code below shows the ids, so you can make sure that you're deleting everything related to the given ID.
MATCH (node)-[relation:HAS]->(value)
where ID(node)=1234
RETURN ID(instance), ID(value), ID(r)
Ps.: ":HAS" is an example of an relationship.

how do i delete all relationship of a specific type in Neo4j

I am new to Neo4j // Cypher and I am following the tutorial.
Playing with the movie database i tried to delete all the "ACTED_IN" relationship using the following query
match (:Person)-[r:ACTED_IN]->(:Movie)
DELETE r;
however i found that i have i still have some "ACTED_IN" relations between nodes and i have to re-run the previous query several times to completely remove those relations.
why is it not working as i expected?
what is the right way to do this?
thanks
Just tried, it worked for me (Using Neo4j 2.0.1 and 2.1.0-M01)
match (:Person)-[:ACTED_IN]->(:Movie) return count(*);
-> count(*)
172
match (:Person)-[r:ACTED_IN]->(:Movie) delete r;
-> Deleted 172 relationships, returned 0 rows in 172 ms
match (:Person)-[:ACTED_IN]->(:Movie) return count(*);
-> count(*)
0
To delete all 'follows' relations associated with node with name 'vishal1#myemail.com' :
MATCH (n { name:'vishal1#myemail.com' })-[r:follows]->() DELETE r
Worked for me :)
Further, you can also specify label(in my case 'User') to distinguish between nodes with same name
MATCH (n:User { name:'vishal1#myemail.com' })-[r:follows]->() DELETE r
Neo4j Relationshiptypes are case sensitive. So ACTED_IN and acted_in will act as different relationshipTypes

Neo4j: Get all nodes in a graph, even those that are unconnected by relationships

Using Cypher how can I get all nodes in a graph? I am running some testing against the graph and I have some nodes without relationships so am having trouble crafting a query.
The reason I want to get them all is that I want to delete all the nodes in the graph at the start of every test.
So, this gives you all nodes:
MATCH (n)
RETURN n;
If you want to delete everything from a graph, you can do something like this:
MATCH (n)
OPTIONAL MATCH (n)-[r]-()
DELETE n, r;
Updated for 2.0+
Edit:
Now in 2.3 they have DETACH DELETE, so you can do something like:
MATCH (n)
DETACH DELETE n;
Would this work for you?
START a=node:index_name('*:*')
Assuming you have an index with these orphaned nodes in them.
This just works fine in 2.0:
MATCH n RETURN n
If you need to delete some large number of objects from the graph, one needs to be mindful of the not building up such a large single transaction such that a Java OUT OF HEAP Error will be encountered.
If your nodes have more than 100 relationships per node ((100+1)*10k=>1010k deletes) reduce the batch size or see the recommendations at the bottom.
With 4.4 and newer versions you can utilize the CALL {} IN TRANSACTIONS syntax.
MATCH (n:Foo) where n.foo='bar'
CALL { WITH n
DETACH DELETE n
} IN TRANSACTIONS OF 10000 ROWS;
With 3.x forward and using APOC
call apoc.periodic.iterate("MATCH (n:Foo) where n.foo='bar' return id(n) as id", "MATCH (n) WHERE id(n) = id DETACH DELETE n", {batchSize:10000})
yield batches, total return batches, total
For best practices around deleting huge data in neo4j, follow these guidelines.

Resources