How to delete multiple nodes by specific ID using Cypher - jdbc

Question

I am trying to optimize this cypher query.
I am using neo4j-jdbc
For a given source node and list of target nodes I would like to remove the relationship("follow) between them).
Right now I only found a way to execute them on each transaction:
for example:
source node: 34 and targetNodes: 777
execute:
MATCH (p1:users)-[r:follow]->(p2:users)
WHERE p1.userId='34' and p2.userId='777' and
delete r
java neo4j-jdbc code:
public void deleteNodes(String sourceUserId, Set<String> userIdsList) {
try {
conn = neo4jDataSource.openConnection();
conn.setAutoCommit(false);
newUserDistanceList.forEach(user -> {
try {
this.deleteRelationship(sourceUserId, user.getUserId());
} catch (SQLException e) {
throw new RuntimeException("Error deleting relationship for sourceNode=" + sourceUserId + ", targetNode=" + user.getUserId(), e);
}
});
conn.commit();
} catch (Exception e) {
throw new RuntimeException("Error deleting relationship for sourceNode=" + sourceUserId, e);
} finally {
neo4jDataSource.closeConnection(conn);
}
}
public void createNodeAndSetRelationship(String sourceUserId, String targetUserId) throws SQLException {
String deleteUserStmnt =
"MATCH (p1:users)-[r:follow]->(p2:users) "+
"WHERE p1.userId=~{1} and p2.userId=~{2} and "+
"delete r";
try (final PreparedStatement ps1 = conn.prepareStatement(deleteUserStmnt)) {
ps1.setString(1, sourceUserId);
ps1.setString(2, targetUserId);
ps1.executeQuery();
}
}
How would you optimize this into one query to include it all? is it even possible?
*P.S please add any other notes about this code if you find them helpful.
Response to comments:
I added my nodes this way:
MERGE (p1:C10{userId:'1'})
MERGE (p2:C10{userId:'2'})
MERGE (p3:C10{userId:'3'})
MERGE (p1)-[r1:follow]->(p2)
MERGE (p1)-[t1:follow]->(p3)
When executing the delete query nothing is being deleted:
MATCH (user1:C10 {userId: 1})-[r:follow]->(users:C10) WHERE
users.userId in [3, 2] DELETE r
userId is unique property on each node
Any idea?
Thank you,
ray.

Answer 1

Query
Let's create some data to test that our query will work.
CREATE (user1:User {id: "1"})
CREATE (user2:User {id: "2"})
CREATE (user3:User {id: "3"})
CREATE (user1)-[:FOLLOW]->(user2)
CREATE (user1)-[:FOLLOW]->(user3)
How our data looks right now:
Let's write query to delete :FOLLOW relationship from between user1 and user2 and user3:
MATCH (user1:User {id: "1"})-[r:FOLLOW]->(users:User)
WHERE users.id in ["2", "3"]
DELETE r
Now relationship's are gone:
Good luck :)
Note: this works with strings too.
Note2: you should check that index (or event constraint) exists for your userId property on :user nodes.
neo4j-jdbc
Code sample for neo4j-jdbc that does work:
Class.forName("org.neo4j.jdbc.Driver");
Connection connection = DriverManager.getConnection("jdbc:neo4j://localhost:7474/");
String removeRelationships = "MATCH (user1:User {id: {1}})-[r:FOLLOW]->(users:User) " +
"WHERE users.id in {2} " +
"DELETE r";
try (final PreparedStatement stmt = connection.prepareStatement(removeRelationships)) {
stmt.setObject(1, "1");
stmt.setObject(2, new ArrayList<Integer>() {{
add("2");
add("3");
}});
stmt.executeQuery();
}