[GENERAL] BDR replication and table triggers

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От jamesadams89
Тема [GENERAL] BDR replication and table triggers
Дата
Msg-id 1493210883978-5958463.post@n3.nabble.com
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Ответы Re: [GENERAL] BDR replication and table triggers
Re: [GENERAL] BDR replication and table triggers
Список pgsql-general
Hi,

I have some questions regarding how BDR interacts with triggers.

I have two databases that are both joined to the same BDR group and
correctly replicating between one another sharing a table created as:

create table testtable(
    key varchar(16) NOT NULL PRIMARY KEY,
    data jsonb
);

With the following trigger defined:

CREATE OR REPLACE FUNCTION test_table_notify()
RETURNS TRIGGER AS
$$
BEGIN
    IF TG_OP='INSERT' OR TG_OP='UPDATE' THEN
        PERFORM pg_notify( 'TestTable', TG_OP || ' ' || NEW.key );
    ELSE
        PERFORM pg_notify( 'TestTable', TG_OP || ' ' || OLD.key );
    END IF;
    RETURN NULL;
END;
$$ LANGUAGE plpgsql;


CREATE TRIGGER TestTableTrigger
AFTER INSERT OR UPDATE OR DELETE
on testtable
FOR EACH ROW
EXECUTE PROCEDURE test_table_notify();

I then have a client application listening on the 'TestTable' Notify on one
of the Databases:

Client
 ___
|     |
| A  |
|___|
  /\
   |
 _|_         ___
|      |     |       |
|DB1|-----|DB2|
|_ __|     |____|

If I perform any INSERT, UPDATE or DELETE operations directly on DB1 I see
the trigger on the table being fired as expected and Client Application 'A'
recieves the notify.  I also see the changes propagate to DB2 via BDR as
expected.  However if I perform any INSERT, UPDATE or DELETE operations on
DB2 and these changes propagate over to DB1 via BDR I do not see DB1 firing
any triggers. Is this intended behavior?  My current understanding is that
BDR is unable to invoke Postgres triggers as it operates on the rows
directly, a layer below Postgres. Is this Correct? Is there any mechanism
that exists that could provide notifications to a listening application when
BDR makes changes to the underlying database?

Apologies if this is all a bit elementary, this is my first foray into BDR
and I was unable to find anything in the documentation that mentioned
triggers.

Thanks for any input



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