Raised when an EVENT TRIGGER function violates the required output protocol.
event_trigger_protocol_violated (PostgreSQL 39P03) means the EVENT TRIGGER function did not return result rows in the mandatory format. Ensure the function emits "tag" text first and obeys the expected column order, or drop and recreate the trigger with a compliant function.
event_trigger_protocol_violated
PostgreSQL throws error 39P03 when an EVENT TRIGGER function fails to follow the strict row-return protocol expected by the server.
The function must emit result rows whose first column is the command tag text; any deviation triggers event_trigger_protocol_violated and aborts the firing event.
Most cases arise from PL/pgSQL functions that mistakenly return a different composite type, omit required columns, or output columns in the wrong order.
Returning NULL instead of the expected text tag column also violates the protocol and raises 39P03 immediately.
Using "RETURN NEXT" with a mismatched record structure or selecting from a table rather than building the mandated record triggers the same exception.
Audit the EVENT TRIGGER function definition first.
Verify that the returned record type starts with a TEXT column named "tag" followed by JSONB or TEXT fields if used.
Recreate the function with correct OUT parameters, then attach it back to the EVENT TRIGGER. Test with simple DDL to confirm the error is gone.
After upgrading PostgreSQL, previously valid trigger functions may break because newer versions enforce stricter protocol checks.
Add the missing "tag" column to fix.
Copy-pasting a table-returning function into an EVENT TRIGGER often causes 39P03.
Replace "RETURNS TABLE" with "RETURNS EVENT_TRIGGER" and build a proper record.
Always use RETURNS EVENT_TRIGGER in PL/pgSQL for event triggers and follow the official example in the docs.
Add unit tests that run CREATE TABLE and ALTER TABLE inside a transaction to surface protocol violations during development.
error 39P01 invalid_savepoint_specification appears when SAVEPOINT usage is wrong.
Correct nesting to resolve.
error 42P01 undefined_table is common when the trigger function refers to a missing table. Create or qualify the table properly.
.
No. The server cancels the triggering command. You must correct the function or disable the trigger.
Yes. Versions 13+ enforce stricter checks, so older functions may fail after upgrade.
Galaxy's linting highlights mismatched RETURN types and lets teams endorse tested trigger functions, reducing protocol errors.
Dropping an EVENT TRIGGER does not affect table data. Only the auditing or logging logic is removed.
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