Triggers

A trigger automatically executes predefined operations in response to specific data events. Triggers run before an insert or update operation, allowing you to enforce business rules, maintain data integrity, or perform auxiliary operations without manual intervention.

Showing Triggers

Show triggers in the current graph:

GQL
SHOW TRIGGERS

-- Filter by node label
SHOW TRIGGERS ON NODE Student

-- Filter by edge label
SHOW TRIGGERS ON EDGE "ATTENDS"

Returns a table with the following columns:

Creating Triggers

Syntax
<create trigger statement> ::=
  "CREATE TRIGGER" [ "IF NOT EXISTS" ] <trigger name> "ON" < "NODE" | "EDGE" > <label name> 
  [ "COMMENT" <comment> ]
  "BEFORE" < "INSERT" | "UPDATE" >
  "CALL" <callable body string>

Details

• BEFORE INSERT only fires for nodes. BEFORE UPDATE fires normally on both nodes and edges.

Callable Body

The <callable body> uses the format $entity call { ... } and supports let assignments to modify entity properties. The let keyword must be lowercase.

Syntax
<callable body> ::=
  "$entity call {" <let assignment>, { ";" <let assignment> }... "}"

<let assignment> ::=
  "let entity." <property name> "=" <value expression>

Supported value expressions:

Limitations of the callable body

The body language is intentionally narrow. Be aware of the following:

• Only let entity.<property> = <expression> assignments are supported. There are no statements for conditionals, loops, explicit REJECT/ABORT, logging, or calls to user-defined procedures.
• Only the properties of the triggering entity are reachable via entity.<property>. Other nodes, edges, parameters, and graph state cannot be queried from inside the body.

Examples

GQL
-- BEFORE INSERT node trigger: normalize student name and set default status
CREATE TRIGGER "InitStudent" ON NODE "Student"
  COMMENT 'Normalize name and set default status'
  BEFORE INSERT
  CALL " $entity call { let entity.name = upper(trim(entity.name)); let entity.status = 'active' } "

-- Now inserting a Student node will uppercase the name and set status
INSERT (n:Student {name: "John Doe"})
RETURN n.name, n.status   // "JOHN DOE", "active"

GQL
-- BEFORE UPDATE node trigger: normalize user email
CREATE TRIGGER "NormalizeEmail" ON NODE "User"
  COMMENT 'Normalize email on update'
  BEFORE UPDATE
  CALL " $entity call { let entity.email = lower(trim(entity.email)) } "

-- Now updating a User's email will trim whitespace and lowercase it
MATCH (u:User {_id: 'u1'})
SET u.email = "  [email protected]  "
RETURN u.email   // "[email protected]"

GQL
-- BEFORE INSERT trigger: stamp creation time and capture the logged-in user
CREATE TRIGGER "InitEmployee" ON NODE "Employee"
  COMMENT 'Audit fields on creation'
  BEFORE INSERT
  CALL " $entity call { let entity.creationDate = now(); let entity.creatorName = CURRENT_USER.username } "

-- Inserting an Employee now auto-stamps audit fields
INSERT (e:Employee {name: 'Alice'})
RETURN e.creationDate, e.creatorName   // 2026-06-03T..., "admin"

Dropping Triggers

Drop the trigger InitStudent:

GQL
DROP TRIGGER "InitStudent"

The IF EXISTS clause is used to prevent errors when attempting to delete a trigger that does not exist. It allows the statement to be safely executed.

GQL
DROP TRIGGER IF EXISTS "InitStudent"

This deletes the trigger InitStudent only if a trigger with that name does exist. If InitStudent does not exist, the statement is ignored without throwing an error.

NOTE

Dropping a label will also remove any triggers associated with that label.

Execution Behavior

• When multiple triggers are defined on the same label and event, they execute in creation order. Each trigger receives the modified properties from the previous trigger.
• When an entity has multiple labels, triggers execute in the order the labels appear in the query. For example, INSERT (:Student&Person {...}) fires Student triggers first, then Person triggers. The modified properties from one label's triggers are passed to the next label's triggers.
• There is no practical way to conditionally veto an operation. The built-in functions (upper, lower, trim, len/length) silently pass through non-string inputs without raising an error, and the body language has no conditional or reject keyword.
• If the body itself errors (for example, calling an undefined function), the operation is aborted and the error is returned to the client.