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})
Related
I want to Delete this Pessoa node and its relations to others,
but I don't want to delete the other nodes.
This node has a Guid ID property with value c40f314f-0ecf-42e1-b44d-85b6d72f134a
I tried
MATCH (n {ID: 'c40f314f-0ecf-42e1-b44d-85b6d72f134a'}) DELETE n;
But this ERROR appears:
Neo.ClientError.Schema.ConstraintValidationFailed: Cannot delete node<35>, because it still has relationships. To delete this node, you must first delete its relationships.
Using
MATCH (n {ID: 'c40f314f-0ecf-42e1-b44d-85b6d72f134a'}) DETACH DELETE n;
Deleted 1 node, deleted 2 relationships, completed after 2 ms.
Note that relationships of the node were removed as well.
I have created a large graph in Neo4j and have an empty node that is connected via 11 million relationships in graph that I need to remove. I know that if I just delete the node I will leave behind all the hanging relationships but I have been unsuccessful in my attempts to remove them. I have tried the following CYPHER commands but they hang and fail to complete:
MATCH (n:Label {uid: ''}) DETACH DELETE n;
and
MATCH (n:Label {uid: ''})-[r]-() DELETE r;
I'm working under the assumption that there are not enough resources to load the 11 million relationship subgraph in memory in order to detach and delete the node. Is there any way to loop over the relationships in order to lower the required system resources?
1) You can use apoc.periodic.commit function from the apoc library:
call apoc.periodic.commit(
'MATCH (n:Label {uid: {uid}})-[r]->()
WITH r LIMIT {limit}
DELETE r
RETURN COUNT(r)', {
limit: 1000,
uid: ...
})
2) You can delete the node, and then create it again with apoc.create.node function:
MATCH (n:Label {uid: 2})
WITH n, {labels: labels(n), properties: properties(n)} AS data
DETACH DELETE n
WITH data
CALL apoc.create.node(data.labels, data.properties) yield node AS newNode
RETURN newNode
You could delete the relationships in batches and then delete the node
MATCH (n:Label {uid: ''})-[r]-()
WITH r
LIMIT 1000
DELETE r;
If you run that successively you will delete the relationships in small batches. Play with the limit amount to see what your running system will tolerate resource wise.
If you are on Neo4j 4.0 or above, then this is the best way:
MATCH (n:Label {uid: ''})-[r]-()
CALL {
WITH r
DELETE r
} IN TRANSACTIONS OF 1000 ROWS;
When fetching or when I try to delete a specifc node like
MATCH (p)
where ID(p)=79259223
OPTIONAL MATCH (p)-[r]-()
//drops p's relations
DELETE r,p
I get the following error
While loading relationships for Node[79259223] a Relationship[87331456] was encountered that had startNode: 80312215 and endNode: 83719851, i.e. which had neither start nor end node as the node we're loading relationships for
I also run the ConsistencyChecker what resulted in a big list of inconsistencys. However how can you fix these inconsistencys? I can not delete the nodes for instance
Here is a possible way to "fix" an occurrence of this error. Unfortunately, it is a fairly manual approach that has to be used for every node that encounters the same problem.
Before you delete the node, you can try to delete the inconsistent relationship by its native neo4j ID. For example:
MATCH ()-[r]->()
WHERE ID(r) = 87331456
DELETE r;
NOTE: Before deleting that relationship, you should first try to take a look at it (e.g., replace DELETE WITH RETURN) to understand what you are planning to delete. You may want to do something else first or instead.
If that deletion works, then try to delete the node again, as follows:
MATCH (p)
WHERE ID(p) = 79259223
DETACH DELETE p;
Notice that I use the DETACH DELETE syntax, which will attempt to delete all the relationships for the specified node.
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;
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.