neo4j - Move/copy all relationships to different node

Question

Is there any way to copy or move a relationship from one node to another?

I have a situation similar to that here:

neo4j merge 2 or multiple duplicate nodes

and here:

Copy relationships of different type using Cypher

Say I have this pattern in the graph

(a)-[r:FOO]->(b)
(a)<-[r2:BAR]-(c)

I then have another node, (d), which may or may not be a duplicate of (a). My thinking is that it does not matter whether the nodes are duplicate or not from a functionality point of view. I want to be able to move or copy the relationships r:FOO and r2:BAR so that the graph now includes

(d)-[r:FOO]->(b)
(d)<-[r2:BAR]-(c)

If I was then doing this to merge nodes when I have duplicates I would like to be able to move the relationships as opposed to copy and then (perhaps optionally) delete (a). Note that there is more than one relationship type and I do not know for sure what the types will be. I realise I can do this in stages but thought it would be great if there was an efficient way to do it in one cypher query. My current strategy is something like (not exact syntax but just to give an idea)

// get all outgoing relationships
MATCH (a:Label1 { title : 'blah' })-[r]->(o)
RETURN r
// returns FOO and BAR

// for each relationship type, create one from (d) and copy the properties over
MATCH (a:Label1 { title : 'blah' })-[r:FOO]->(o), (d:Label1 { title : 'blah blah' })
CREATE (d)-[r2:FOO]->(o)
SET r2 = r
...etc...

// now do the same for incoming relationships
MATCH (a:Label1 { title : 'blah' })<-[r]-(o)
RETURN r
// returns FOO and BAR
// for each relationship type, create one from (d) and copy the properties over
MATCH (a:Label1 { title : 'blah' })<-[r:FOO]-(o), (d:Label1 { title : 'blah blah' })
CREATE (d)<-[r2:FOO]-(o)
SET r2 = r
...etc...

// finally delete node and relationships (if required)
MATCH (a:Label1 { title : 'blah' })-[r]-(o)
DELETE r, a

However this relies on a number of queries and hence transactions. It would be much preferable (in my simpleton view) to be able to achieve this in one query. However, I do not believe anything like this exists in cypher. Am I wrong?

Any ideas? Let me know if this is not clear and I shall try to elaborate and explain further.

For info, I am using Neo4j 2.1.6 community edition (with neo4jclient from a .NET application).

Just realised that I would also have to repeat my process to account for the direction of the relationship unless I am mistaken? i.e. get all outgoing relationships from (a), recreate them as outgoing from (d), and then do the same for all incoming relationships. Cypher above has been edited accordingly.

UPDATE: I am guessing this is a pipe dream and not at all possible. Can anyone confirm this? It would be good to have a definitive answer even if it is "No!". If so I would consider asking the Neo4j guys if this functionality is even feasible and worth considering.

UPDATE 2: From the lack of ideas I am guessing this can't be done. I certainly have got no further in my research or experimentation. Looks like a feature request is the way to go. I can't be the only person who would find this functionality exceptionally useful.

Answer 1

I think you can just chain these together:

// get all relationships
MATCH
  (a:Label1 { title : 'blah' })-[r]-(o),
  (d:Label1 { title : 'blah blah' })
CREATE (d)-[r2:type(r)]-(o)
DELETE r, a

The only thing I'm not entirely sure about is the ability to use the type() function where it's being used there. I'll try it out now