CREATE_EVENT_TRIGGER(7pg16)

💅 CREATE EVENT TRIGGER

okay bestie, so this is the <pink>PostgreSQL 16.15 Documentation</pink> page for CREATE EVENT TRIGGER — aka the glow-up where you teach your database to react to stuff happening. main character energy fr fr 💖

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✨ SYNOPSIS ✨

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

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🦋 DESCRIPTION 🦋

So CREATE EVENT TRIGGER literally creates a brand-new event trigger. the way it works: whenever the <italic>designated event</italic> happens and the WHEN condition attached to the trigger (if there even is one) is satisfied, the trigger function gets executed. simple as that, no cap ✨

If you want the full backstory on event triggers in general, chapter 40 is right there waiting for you. and bestie — the user who creates the event trigger becomes its owner. it's giving "you built it, you own it" 💅

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🎀 PARAMETERS 🎀

• name — the name you're giving your shiny new trigger. it has to be unique within the database, no duplicates allowed 🙅‍♀️
• event — the name of the event that triggers a call to the given function. section 40.1 has all the tea on event names 🔥
• filter_variable — the name of a variable you use to filter events. this is what lets you restrict the firing of the trigger down to a subset of the cases where it's supported. currently the only supported filter_variable is TAG 👑
• filter_value — a list of values for the associated filter_variable that should make the trigger fire. for TAG, that means a list of command tags — like 'DROP FUNCTION' for example 💖
• function_name — a user-supplied function, declared as taking no argument and returning type event_trigger.

and here's the fine print, bestie: in the syntax of CREATE EVENT TRIGGER, the keywords FUNCTION and PROCEDURE are equivalent — BUT the referenced function must in any case be a function, not a procedure. the keyword PROCEDURE here is historical and deprecated, so like… it's giving vintage, but not in a cute way 😭

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🌸 NOTES 🌸

• only superusers can create event triggers. that's the vibe check, and not everybody passes it 🫶
• event triggers are disabled in single-user mode (peep postgres(1) for that one). and if a messed-up event trigger disables the database so badly that you can't even drop the trigger? restart in single-user mode and you'll be able to do it. rescue mission, slay 💀✨

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🔥 EXAMPLES 🔥

forbid the execution of any DDL command — iconic behaviour, honestly:

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();

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🌈 COMPATIBILITY 🌈

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

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⭐ 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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🦋 and that's the whole page, bestie! brought to you by PostgreSQL 16.15, dated 2026 — go forth and trigger responsibly, mwah 💖🎀👑