Triggers

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

CREATE TRIGGER

Syntax
CREATE TRIGGER "triggerName" ON NODE "labelName"
  [COMMENT 'description']
  BEFORE|AFTER INSERT
  CALL " $entity call { ... } "

triggerName: The identifier for the trigger, must be unique within the graph.
labelName: The node label the trigger is associated with. The label does not need to exist at creation time; the trigger will not fire until the label is created.
COMMENT: An optional description of what the trigger does.
BEFORE|AFTER INSERT: When the trigger fires relative to the insert operation.
CALL: The callable body that defines the trigger logic.

Timing

BEFORE INSERT: Fires before the node is inserted. Can modify entity properties. If the trigger returns an error, the insert is aborted.
AFTER INSERT: Fires after the node is inserted. Executes for side effects only. Errors are logged but do not roll back the already-committed insert.

Callable Body

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

Single Assignment
$entity call { let entity.propertyName = expression }

Multiple assignments can be separated by semicolons:

Multiple Assignments
$entity call { 
  let entity.name = upper(entity.name); 
  let entity.role = 'employee' 
}

Supported Expressions

Expression Type	Example	Description
String literal	`'active'`, `"active"`	A quoted string value.
Numeric literal	`18`, `3.14`	An integer or float value.
Property access	`entity.name`	Reads a property from the current entity.
Function call	`upper(entity.name)`	Applies a built-in function to an expression.

Built-in Functions

Function	Description
`upper(value)`	Converts a string to uppercase.
`lower(value)`	Converts a string to lowercase.
`trim(value)`	Removes leading and trailing whitespace from a string.
`len(value)` / `length(value)`	Returns the length of a string.

Examples

Create a trigger that converts the name property to uppercase before insertion:

GQL
CREATE TRIGGER "AutoUpperCase" ON NODE "Student"
  COMMENT 'Converts name to uppercase before insertion'
  BEFORE INSERT
  CALL " $entity call { let entity.name = upper(entity.name) } "

Now inserting a Student node will automatically uppercase the name:

GQL
INSERT (n:Student {name: "John Doe"}) RETURN n.name

n.name
JOHN DOE

Create a trigger that sets a default property value:

GQL
CREATE TRIGGER "DefaultRole" ON NODE "Employee"
  COMMENT 'Sets default role to intern'
  BEFORE INSERT
  CALL " $entity call { let entity.role = 'intern' } "

DROP TRIGGER

Syntax
-- Drop a trigger (error if not found)
DROP TRIGGER "triggerName"

-- Drop only if it exists (no error if not found)
DROP TRIGGER IF EXISTS "triggerName"

NOTE

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

SHOW TRIGGERS

Syntax
-- List all triggers in the current graph
SHOW TRIGGERS

-- Filter by node label
SHOW TRIGGERS ON NODE "labelName"

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

Returns a table with the following columns:

Field	Description
`name`	The name of the trigger.
`entity_type`	The entity type: `NODE`.
`label`	The node label the trigger is associated with.
`event`	The trigger event, such as `BEFORE_INSERT` or `AFTER_INSERT`.
`enabled`	Whether the trigger is active.
`comment`	The optional description of the trigger.

Execution Behavior

When multiple triggers match the same event, they execute sequentially. Each trigger receives the modified properties from the previous trigger.
BEFORE INSERT triggers can modify entity properties. If a BEFORE trigger fails, the insert is aborted.
AFTER INSERT triggers execute for side effects. If an AFTER trigger fails, the error is logged but the insert is not rolled back.
When a node has multiple labels, triggers execute for each label independently.