How to calculate mutual friends with neo4j?

Question

I want to use neo4j to manage relationship among users.

How can I get mutual friends using it?

score 4 · Answer 1 · answered Jun 19 '12 at 05:50

In case of using cypher the following query returns mutual friends:

start a = node(1), b = node(4) match (a)--(x)--(b) return x;

The example above returns mutual friends of node 1 and 4

enter image description here

Below is the copy of queries and its results for the example from the picture:

neo4j-sh (0)$ start a = node(1), b = node(4) match (a)--(x)--(b) return x;
==> +--------------------+
==> | x                  |
==> +--------------------+
==> | Node[3]{Name->"C"} |
==> +--------------------+
==> 1 row
==> 9 ms
==> 
neo4j-sh (0)$ start a = node(1), b = node(6) match (a)--(x)--(b) return x;
==> +--------------------+
==> | x                  |
==> +--------------------+
==> | Node[5]{Name->"E"} |
==> | Node[2]{Name->"B"} |
==> +--------------------+
==> 2 rows
==> 0 ms

in case we dont know the `b` node at the start, we can use `START a=node(1) MATCH a--x--b WHERE a--b RETURN x` — ulkas, Jul 24 '14 at 08:10

score 4 · Accepted Answer · answered Jun 12 '11 at 23:21

The easiest way would be to use the shortest path algorithm of length 2, with the two users, across FRIEND_OF relationships. Those are the paths that connect the two users via exactly one friend hop.

PathFinder<Path> finder = GraphAlgoFactory.shortestPath(
        Traversal.expanderForTypes( FRIEND_OF ), 2 );
Iterable<Path> paths = finder.findAllPaths( user1, user2 );

How to calculate mutual friends with neo4j?

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