Re: logical decoding and replication of sequences, take 2

On Thu, Jul 20, 2023 at 8:22 PM Tomas Vondra
<tomas.vondra@enterprisedb.com> wrote:
>
> OK, I merged the changes into the patches, with some minor changes to
> the wording etc.
>

I think we can do 0001-Make-test_decoding-ddl.out-shorter-20230720
even without the rest of the patches. Isn't it a separate improvement?

I see that origin filtering (origin=none) doesn't work with this
patch. You can see this by using the following statements:
Node-1:
postgres=# create sequence s;
CREATE SEQUENCE
postgres=# create publication mypub for all sequences;
CREATE PUBLICATION

Node-2:
postgres=# create sequence s;
CREATE SEQUENCE
postgres=# create subscription mysub_sub connection '....' publication
mypub with (origin=none);
NOTICE:  created replication slot "mysub_sub" on publisher
CREATE SUBSCRIPTION
postgres=# create publication mypub_sub for all sequences;
CREATE PUBLICATION

Node-1:
create subscription mysub_pub connection '...' publication mypub_sub
with (origin=none);
NOTICE:  created replication slot "mysub_pub" on publisher
CREATE SUBSCRIPTION

SELECT nextval('s') FROM generate_series(1,100);

After that, you can check on the subscriber that sequences values are
overridden with older values:
postgres=# select * from s;
 last_value | log_cnt | is_called
------------+---------+-----------
         67 |       0 | t
(1 row)
postgres=# select * from s;
 last_value | log_cnt | is_called
------------+---------+-----------
        100 |       0 | t
(1 row)
postgres=# select * from s;
 last_value | log_cnt | is_called
------------+---------+-----------
        133 |       0 | t
(1 row)
postgres=# select * from s;
 last_value | log_cnt | is_called
------------+---------+-----------
         67 |       0 | t
(1 row)

I haven't verified all the details but I think that is because we
don't set XLOG_INCLUDE_ORIGIN while logging sequence values.

--
With Regards,
Amit Kapila.