Обсуждение: Restrictions of channel arg of pg_notofy

Hi everyone!

Can the channel argument derived from the NEW pseudo arg of an INSERT TRIGGER?
In the following trigger function, the
    PERFORM pg_notify(fac);
does not work (LISTEN in psql shows no notification).

Any help welcome.
Thanks, Axel

CREATE TRIGGER new_event_trigger AFTER INSERT OR UPDATE ON syslog.event
    FOR EACH ROW EXECUTE PROCEDURE syslog.new_event_action();


CREATE OR REPLACE FUNCTION syslog.new_event_action() RETURNS trigger
    LANGUAGE plpgsql
    AS $$
    DECLARE
        fac TEXT := format('f0%s', NEW.facility);
    BEGIN
    IF NEW.facility > 9 THEN
        fac := format('f%s', NEW.facility);
    END IF;
    IF NEW.facility = 8 THEN
        INSERT INTO pf_event (id) VALUES (NEW.id);
    END IF;
    PERFORM pg_notify(fac);
    RETURN NEW;
    END;
$$;

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PGP-Key:29E99DD6  ☀  computing @ chaos claudius

Axel Rau <Axel.Rau@Chaos1.DE> writes:
> Can the channel argument derived from the NEW pseudo arg of an INSERT TRIGGER?
> In the following trigger function, the
>     PERFORM pg_notify(fac);
> does not work (LISTEN in psql shows no notification).

That should work.

I think more likely what you're running into is that the NOTIFY won't
be delivered until end of transaction?

            regards, tom lane

Axel Rau <Axel.Rau@chaos1.de> writes:
> I have investigated further:
> pg_notify does not work at all, even with a constant string channel arg.
> NOTIFY works.
> This is release 11.2.

[ shrug... ]  Works for me.

> What am I doing wrong?

Hard to tell when you haven't provided a complete example.

Just looking at the code you did show, though, I notice that
you have

    PERFORM pg_notify(fac);

but there's no single-argument form of pg_notify in standard PG:

regression=# \df pg_notify
                           List of functions
   Schema   |   Name    | Result data type | Argument data types | Type 
------------+-----------+------------------+---------------------+------
 pg_catalog | pg_notify | void             | text, text          | func
(1 row)

Maybe whatever shim you've got for that doesn't work right?

            regards, tom lane

Axel Rau <Axel.Rau@Chaos1.DE> writes:
>> Am 28.04.2019 um 19:02 schrieb Tom Lane <tgl@sss.pgh.pa.us <mailto:tgl@sss.pgh.pa.us>>:
>>> Hard to tell when you haven't provided a complete example.

>> This is my test case with constant string:
>> CREATE OR REPLACE FUNCTION syslog.new_event_action() RETURNS trigger
>> LANGUAGE plpgsql
>> AS $$
>> BEGIN
>> RAISE WARNING 'syslog.new_event_action() called.';
>> PERFORM pg_notify('INSERTED', '');
>> RETURN NEW;
>> END
>> $$;
>>
>> The warning is being logged.
>>
>> In psql session 1, I run a LISTEN INSERTED;

If you're typing it exactly like that, you have a case-folding problem.
Try
    LISTEN "INSERTED";
instead, or make the pg_notify argument lower-case.

However, that doesn't seem like it would explain your original problem,
since that didn't involve upper-case letters.

            regards, tom lane

Am 28.04.2019 um 20:23 schrieb Tom Lane <tgl@sss.pgh.pa.us>:

>
> If you're typing it exactly like that, you have a case-folding problem.
> Try
>     LISTEN "INSERTED";
> instead, or make the pg_notify argument lower-case.
Oh, I see. The constant string case now works if both LISTEN and pg_notify args are lower case.
This was an important hint.
>
> However, that doesn't seem like it would explain your original problem,
> since that didn't involve upper-case letters.
The original problem could also be resolved by ensuring same case and listen for currect facility. (-;

Thanks for your patience,
Axel
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PGP-Key:29E99DD6  ☀  computing @ chaos claudius