Hi,
out of curiosity I created the following setup, all with
9.6 and pglogical.
D1 is configured as provider with a replication set that
contains only 1 table. Only inserts are replicated.
D2 is configured as subscriber for that replication set.
Replication works, all inserts on D2 arrive also on D2.
Now, I add the following always firing trigger to the
table:
CREATE OR REPLACE
FUNCTION notify.trgfn () RETURNS trigger AS $def$
BEGIN
PERFORM pg_notify(NEW.channel, NEW.msg);
RETURN NULL;
END
$def$ LANGUAGE plpgsql;
CREATE TRIGGER trg BEFORE INSERT ON notify.notify
FOR EACH ROW
EXECUTE PROCEDURE notify.trgfn();
ALTER TABLE notify.notify ENABLE ALWAYS TRIGGER trg;
As you can see, the trigger function should prevent the
actual insert and only call pg_notify(). In principle this
works but there is a catch. Notifications generated this way
are only delivered after another notification genuinely
generated on the subscriber node. The channel of this
notification does not matter. If I replace PERFORM pg_notify() by
RAISE NOTICE I see
the message immediately in the log.
First I thought this is related to session_replication_role=replica. So,
I tried the direct insert on D2 with this setting using psql.
The notification was fired immediately. Also, whether the
trigger prevents or allows the actual insert does not matter.
I tried to create the trigger function as SECURITY DEFINER and
with a specific search_path. That didn't help either.
By now I am thinking there must be something missing in
pglogical.
Thanks,
Torsten
