Supported Versions: Current (12) / 11 / 10 / 9.6 / 9.5 / 9.4
Development Versions: devel
Unsupported versions: 9.3 / 9.2 / 9.1 / 9.0 / 8.4 / 8.3 / 8.2 / 8.1 / 8.0 / 7.4 / 7.3
This documentation is for an unsupported version of PostgreSQL.
You may want to view the same page for the current version, or one of the supported versions listed above instead.

40.2. Trigger Functions

When a function is used in a trigger, the dictionary TD contains trigger-related values. The trigger rows are in TD["new"] and/or TD["old"] depending on the trigger event. TD["event"] contains the event as a string (INSERT, UPDATE, DELETE, or UNKNOWN). TD["when"] contains one of BEFORE, AFTER, and UNKNOWN. TD["level"] contains one of ROW, STATEMENT, and UNKNOWN. TD["name"] contains the trigger name, and TD["relid"] contains the OID of the table on which the trigger occurred. If the trigger was called with arguments they are available in TD["args"][0] to TD["args"][(n-1)].

If TD["when"] is BEFORE, you may return None or "OK" from the Python function to indicate the row is unmodified, "SKIP" to abort the event, or "MODIFY" to indicate you've modified the row.