44.5. 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, orTRUNCATE. -
TD["when"] -
contains one of
BEFORE,AFTER, orINSTEAD OF. -
TD["level"] -
contains
ROWorSTATEMENT. -
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 TRIGGERcommand included arguments, they are available inTD["args"][0]toTD["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.