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.