CREATE_EVENT_TRIGGER(7pg13)

💅 CREATE EVENT TRIGGER 💅

okay so real quick — this page is CREATE EVENT TRIGGER(7) from the PostgreSQL 13.23 Documentation, and it's literally the glow-up guide for making things happen automatically when stuff goes down in your database. bestie, let's get into it 🎀

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✨ NAME ✨

CREATE_EVENT_TRIGGER — define a new event trigger 👑

🌸 SYNOPSIS 🌸

CREATE EVENT TRIGGER name
    ON event
    [ WHEN filter_variable IN (filter_value [, ... ]) [ AND ... ] ]
    EXECUTE { FUNCTION | PROCEDURE } function_name()

🦋 DESCRIPTION 🦋

so CREATE EVENT TRIGGER creates a brand new event trigger, no cap. the way it works: whenever the designated event happens and the WHEN condition that's attached to the trigger (if there even is one) is satisfied, the trigger function gets executed. periodt. 💖

if you want the whole general introduction to event triggers, that lives in Chapter 39 — go read it, iykyk.

and here's a cute little detail: the user who creates an event trigger becomes its owner. main character energy, honestly. 🌈

💜 PARAMETERS 💜

• name — the name you're giving your new trigger. it has to be unique within the database, so no copy-paste names, bestie 🙈
• event — the name of the event that triggers a call to the given function. Section 39.1 has all the deets on event names ✨
• filter_variable — the name of a variable that's used to filter events. this is how you restrict the trigger so it only fires for a subset of the cases where it's supported — lowkey so useful. currently the only supported filter_variable is TAG 🏷️
• filter_value — a list of values for the associated filter_variable that you want the trigger to fire for. for TAG, that means a list of command tags (like 'DROP FUNCTION') 💅
• function_name — a user-supplied function that's declared as taking no argument and returning type event_trigger.

and here's the tea ☕ — in the syntax of CREATE EVENT TRIGGER, the keywords FUNCTION and PROCEDURE are equivalent, but the referenced function has to be a function in any case, not a procedure. the PROCEDURE keyword here is historical and highkey deprecated, so yeah, watch out for that 🫶

⚠️ fr fr: even though the syntax lets you say PROCEDURE, whatever you point at must actually be a function. don't get caught out.

🔥 NOTES 🔥

• ngl, only superusers can create event triggers. that's just how it is 👑
• event triggers are disabled in single-user mode (peep postgres(1)). and if some erroneous event trigger disables your database so hard that you can't even drop the trigger?? restart in single-user mode and you'll be able to do it. lifesaver, honestly 😭💖

🍓 EXAMPLES 🍓

want to forbid the execution of any DDL command? iconic. here's how:

CREATE OR REPLACE FUNCTION abort_any_command()
  RETURNS event_trigger
 LANGUAGE plpgsql
  AS $$
BEGIN
  RAISE EXCEPTION 'command % is disabled', tg_tag;
END;
$$;

CREATE EVENT TRIGGER abort_ddl ON ddl_command_start
   EXECUTE FUNCTION abort_any_command();

slay 💅 that's the whole vibe.

🌸 COMPATIBILITY 🌸

there is no CREATE EVENT TRIGGER statement in the SQL standard. we're built different 🦋

⭐ SEE ALSO ⭐

• ALTER EVENT TRIGGER (ALTER_EVENT_TRIGGER(7))
• DROP EVENT TRIGGER (DROP_EVENT_TRIGGER(7))
• CREATE FUNCTION (CREATE_FUNCTION(7))

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okay that's the whole page, bestie, you're officially caught up 🫶✨

this came from the PostgreSQL 13.23 Documentation, dated 2025, and that's the CREATE EVENT TRIGGER(7) page — go forth and trigger responsibly 💜👑