apoc.trigger.show

Procedure APOC Core

CALL apoc.trigger.show(databaseName) | it lists all eventually installed triggers for a database

Signature

apoc.trigger.show(databaseName :: STRING?) :: (name :: STRING?, query :: STRING?, selector :: MAP?, params :: MAP?, installed :: BOOLEAN?, paused :: BOOLEAN?)

Input parameters

Name	Type	Default
databaseName	STRING?	null

Name

Type

Default

databaseName

STRING?

null

Output parameters

Name	Type
name	STRING?
query	STRING?
selector	MAP?
params	MAP?
installed	BOOLEAN?
paused	BOOLEAN?

Name

Type

name

STRING?

query

STRING?

selector

MAP?

params

MAP?

installed

BOOLEAN?

paused

BOOLEAN?

Enable Triggers

By default triggers are disabled. We can enable them by setting the following property in apoc.conf:

apoc.conf

apoc.trigger.enabled=true
apoc.trigger.refresh=60000

Table 1. Description
Option Key	Value	Description
apoc.trigger.enabled	true/false, default false	Enable/Disable the feature
apoc.trigger.refresh	number, default 60000	Interval in ms after which a replication check is triggered across all cluster nodes

Usage Examples

All these apoc.trigger.* procedures are intended to be executed in the system database, therefore they have to be used executed by opening a system database session. There are several ways of doing this:

when using cypher-shell or Neo4j Browser, one can prefix their Cypher query with :use system
when using fabric, one can prefix their Cypher query with USE system
when using the drivers, one can open a session directly against the system database

Moreover, they accept as first parameter the name of the database towards which we want to install/update/remove the triggers.

Through this implementation, we can use these procedures in a cluster environment, by leveraging the cluster routing mechanism.

These procedures are only executable by a user with admin permissions. If this is not the case, the procedure throws an exception with the message permission has not been granted for user 'xxx'.

Installing, updating or removing a trigger is an eventually consistent operation. Therefore, they are not immediately added/updated/removed, but they have a refresh rate handled by the Apoc configuration apoc.trigger.refresh=<MILLISECONDS>, with default 60000 (milliseconds)

This example assumes that an apoc.trigger.install has already been executed:

CALL apoc.trigger.show('neo4j');

Table 2. Results
name	query	selector	params	installed	paused
"count-removals"	MATCH (c:Counter) SET c.count = c.count + size([f IN $deletedNodes WHERE id(f) 0])	{}	{}	TRUE	FALSE