Re: Single transaction in the tablesync worker?

On Tue, Feb 9, 2021 at 10:38 AM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:

> PSA an alternative patch. This one adds a new member to
> WalRcvExecResult and so is able to detect the "slot does not exist"
> error. This patch also applies on top of V28, if you want it.

Did some testing with this patch on top of v29. I could see that now,
while dropping the subscription, if the tablesync slot does not exist
on the publisher, then it gives a warning
but the command does not fail.

postgres=# CREATE SUBSCRIPTION tap_sub CONNECTION 'host=localhost
dbname=postgres port=6972' PUBLICATION tap_pub WITH (enabled = false);
NOTICE: created replication slot "tap_sub" on publisher
CREATE SUBSCRIPTION
postgres=# ALTER SUBSCRIPTION tap_sub enable;
ALTER SUBSCRIPTION
postgres=# ALTER SUBSCRIPTION tap_sub disable;
ALTER SUBSCRIPTION
=== here, the tablesync slot exists on the publisher but I go and
=== manually drop it.

postgres=# drop subscription tap_sub;
WARNING: could not drop the replication slot
"pg_16401_sync_16389_6927117142022745645" on publisher
DETAIL: The error was: ERROR: replication slot
"pg_16401_sync_16389_6927117142022745645" does not exist
NOTICE: dropped replication slot "tap_sub" on publisher
DROP SUBSCRIPTION

I have a minor comment on the error message, the "The error was:"
seems a bit redundant here. Maybe remove it? So that it looks like:

WARNING: could not drop the replication slot
"pg_16401_sync_16389_6927117142022745645" on publisher
DETAIL: ERROR: replication slot
"pg_16401_sync_16389_6927117142022745645" does not exist

regards,
Ajin Cherian
Fujitsu Australia