45.6. Trigger Functions

When a function is used as a trigger, the dictionary TD contains trigger-related values:

  • TD["event"]

    • contains the event as a string: INSERT , UPDATE , DELETE , or TRUNCATE .
  • TD["when"]

    • contains one of BEFORE , AFTER , or INSTEAD OF .
  • TD["level"]

    • contains ROW or STATEMENT .
  • TD["new"]
    TD["old"]

    • For a row-level trigger, one or both of these fields contain the respective trigger rows, depending on the trigger event.
  • TD["name"]

    • contains the trigger name.
  • TD["table_name"]

    • contains the name of the table on which the trigger occurred.
  • TD["table_schema"]

    • contains the schema of the table on which the trigger occurred.
  • TD["relid"]

    • contains the OID of the table on which the trigger occurred.
  • TD["args"]

    • If the CREATE TRIGGER command included arguments, they are available in TD["args"][0] to TD["args"][n-1] .

If TD["when"] is BEFORE or INSTEAD OF and TD["level"] is ROW , you can return None or "OK" from the Python function to indicate the row is unmodified, "SKIP" to abort the event, or if TD["event"] is INSERT or UPDATE you can return "MODIFY" to indicate you've modified the new row. Otherwise the return value is ignored.