Trigger Functions
| PostgreSQL 9.3.19 Documentation | ||||
|---|---|---|---|---|
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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.