User-defined functions are written in Java, deployed into the database and are called in the same way as any other Cypher function.
This example shows how you invoke a user-defined function called join from Cypher.
This calls the user-defined function org.neo4j.procedure.example.join().
Query.
MATCH (n:Member)
RETURN org.neo4j.function.example.join(collect(n.name)) AS members
| members |
|---|
|
1 row |
|
|
Try this query live. UNWIND ["John", "Paul", "George", "Ringo"] as name CREATE (:Member {name: name}) MATCH (n:Member) RETURN org.neo4j.function.example.join(collect(n.name)) AS members
For developing and deploying user-defined functions in Neo4j, see Extending Neo4j → User-defined functions.
User-defined aggregation functions are written in Java, deployed into the database and are called in the same way as any other Cypher function.
This example shows how you invoke a user-defined aggregation function called longestString from Cypher.