Triggers

TimescaleDB supports the full range of PostgreSQL triggers. Creating, altering, or dropping triggers on a hypertable propagates the changes to all of the underlying chunks.

Create a trigger

This example creates a new table called error_conditions with the same schema as conditions, but that only stores records which are considered errors. An error, in this case, is when an application sends a temperature or humidity reading with a value that is greater than or equal to 1000.

Creating a trigger

1. Create a function that inserts erroneous data into the error_conditions table:

``` 1. CREATE OR REPLACE FUNCTION record_error()

1. RETURNS trigger AS $record_error$

2. BEGIN

3. IF NEW.temperature >= 1000 OR NEW.humidity >= 1000 THEN

4. INSERT INTO error_conditions

5. VALUES(NEW.time, NEW.location, NEW.temperature, NEW.humidity);

6. END IF;

7. RETURN NEW;

8. END;

9. $record_error$ LANGUAGE plpgsql; ```

10. Create a trigger that calls this function whenever a new row is inserted into the hypertable:

``` 1. CREATE TRIGGER record_error

1. BEFORE INSERT ON conditions

2. FOR EACH ROW

3. EXECUTE PROCEDURE record_error(); ```

4. All data is inserted into the conditions table, but rows that contain errors are also added to the error_conditions table.

TimescaleDB supports the full range of triggers, including BEFORE INSERT, AFTER INSERT, BEFORE UPDATE, AFTER UPDATE, BEFORE DELETE, and AFTER DELETE. For more information, see the PostgreSQL docs.