| = Triggers |
| |
| Triggers are identified with a name defined by: |
| |
| [source,bnf] |
| ---- |
| include::example$BNF/trigger_name.bnf[] |
| ---- |
| |
| [[create-trigger-statement]] |
| == CREATE TRIGGER |
| |
| Creating a new trigger uses the `CREATE TRIGGER` statement: |
| |
| [source,bnf] |
| ---- |
| include::example$BNF/create_trigger_statement.bnf[] |
| ---- |
| |
| For instance: |
| |
| [source,cql] |
| ---- |
| include::example$CQL/create_trigger.cql[] |
| ---- |
| |
| The actual logic that makes up the trigger can be written in any Java |
| (JVM) language and exists outside the database. You place the trigger |
| code in a `lib/triggers` subdirectory of the Cassandra installation |
| directory, it loads during cluster startup, and exists on every node |
| that participates in a cluster. The trigger defined on a table fires |
| before a requested DML statement occurs, which ensures the atomicity of |
| the transaction. |
| |
| [[drop-trigger-statement]] |
| == DROP TRIGGER |
| |
| Dropping a trigger uses the `DROP TRIGGER` statement: |
| |
| [source,bnf] |
| ---- |
| include::example$BNF/drop_trigger_statement.bnf[] |
| ---- |
| |
| For instance: |
| |
| [source,cql] |
| ---- |
| include::example$CQL/drop_trigger.cql[] |
| ---- |
