How should I check if two nodes have relationship with each other,in neo4j embedded database in java?

Question

How should I check if two nodes have relationship with each other,in neo4j embedded database in java?

I want the syntax please or a tutorial link,I have seen neo4j website but didn't find it.

Thanks.

Anemology

Answer 1

Given two nodes "nodeA" and "nodeB",

1. gets all relationships attached to "nodeA",

   rels = nodeA.getRelationships();
   

2. iterate through the collection of relationships "rels", for each relationship "rel", test whether the other end node is nodeB

   rel.getOtherNode(nodeA).equals(nodeB)
   

3. if the above expression holds true for one of the relationships, then nodeA and nodeB are connected.

Here is the java API for "Node" and "Relationshiip",

http://api.neo4j.org/current/

Beater

I just thought I would add, that you should consider the edge counts of nodeA and nodeB before performing this search, as you can perform it starting from either node. – Woken

This does not work well if you potentially have many thousands of relationships. – Ensample

Answer 2

private boolean sharedRelationshipExists( Node nodeA, long nodeBId)
{
    Iterator<Relationship> iterator = nodeA.getRelationships().iterator();
    while ( iterator.hasNext() )
    {
        if (iterator.next().getOtherNode( nodeA ).getId() == nodeBId) return true;
    }
    return false;
}

// in another part
boolean sharedRelationshipBetweenAB;
if ( nodeA.getDegree() < nodeB.getDegree() )
{
    sharedRelationshipBetweenAB = sharedRelationshipExists( nodeA, nodeB.getId() );
}
else
{
    sharedRelationshipBetweenAB = sharedRelationshipExists( nodeB, nodeA.getId() );
}

the boolean sharedRelationshipBetweenAB will hold your answer

Brutus