Stored Functions

User-defined Cypher functions with typed parameters, default values, schema namespacing, and body caching. Functions can query the graph, read/write documents, and call other functions (up to 16 levels deep with cycle detection).

CREATE FUNCTION

-- Simple expression function
CREATE FUNCTION greet(name: STRING) RETURNS STRING AS {
  'Hello, ' + name + '!'
}

-- With default parameter
CREATE FUNCTION greet(name: STRING = 'World') RETURNS STRING AS {
  'Hello, ' + name + '!'
}

-- Graph-reading function
CREATE FUNCTION friend_count(person: STRING) RETURNS INT AS {
  MATCH (p:Person {name: person})-[:FRIEND]->(f)
  RETURN count(f)
}

-- Document-reading function
CREATE FUNCTION get_email(username: STRING) RETURNS STRING AS {
  MATCH DOCUMENT d IN auth.users WHERE d.username = username
  RETURN d.email
}

-- Mutating function (writes data)
CREATE FUNCTION log_event(event: STRING) RETURNS VOID MUTATING AS {
  CREATE DOCUMENT IN audit uuid() {
    event: event,
    ts: timestamp()
  }
}

Calling Functions

-- Inline in expressions (non-mutating only)
MATCH (n:Person)
RETURN n.name, greet(n.name)

-- In WHERE clauses
MATCH (n:Person)
WHERE friend_count(n.name) > 5
RETURN n.name

-- With CALL ... YIELD (required for mutating functions)
CALL log_event('user_login') YIELD result

-- CALL with arguments from MATCH
MATCH (n:Person)
CALL greet(n.name) YIELD result
RETURN n.name, result

Management

-- Update existing function
CREATE OR REPLACE FUNCTION greet(name: STRING) RETURNS STRING AS {
  'Hi, ' + name + '!'
}

-- Drop a function
DROP FUNCTION greet

-- List all functions
SHOW FUNCTIONS

-- List functions in a schema
SHOW FUNCTIONS IN auth

Parameter Types

Functions in the auth schema are protected and require admin privileges. Max nesting depth is 16 levels with automatic cycle detection.