Because this feature is now being implemented as a PUBLICATION option,
there is another scenario that might need consideration; I am thinking
about where the same table is published by multiple PUBLICATIONS (with
different option settings) that are subscribed by a single
SUBSCRIPTION.
e.g.1
-----
CREATE PUBLICATION pub1 FOR TABLE t1 WITH (publish_generated_columns = true);
CREATE PUBLICATION pub2 FOR TABLE t1 WITH (publish_generated_columns = false);
CREATE SUBSCRIPTION sub ... PUBLICATIONS pub1,pub2;
-----
e.g.2
-----
CREATE PUBLICATION pub1 FOR ALL TABLES WITH (publish_generated_columns = true);
CREATE PUBLICATION pub2 FOR TABLE t1 WITH (publish_generated_columns = false);
CREATE SUBSCRIPTION sub ... PUBLICATIONS pub1,pub2;
-----
Do you know if this case is supported? If yes, then which publication
option value wins?
The CREATE SUBSCRIPTION docs [1] only says "Subscriptions having
several publications in which the same table has been published with
different column lists are not supported."
Perhaps the user is supposed to deduce that the example above would
work OK if table 't1' has no generated cols. OTOH, if it did have
generated cols then the PUBLICATION column lists must be different and
therefore it is "not supported" (??).
I have not tried this to see what happens, but even if it behaves as
expected, there should probably be some comments/docs/tests for this
scenario to clarify it for the user.
Notice that "publish_via_partition_root" has a similar conundrum, but
in that case, the behaviour is documented in the CREATE PUBLICATION
docs [2]. So, maybe "publish_generated_columns" should be documented
a bit like that.
======
[1] https://www.postgresql.org/docs/devel/sql-createsubscription.html
[2] https://www.postgresql.org/docs/devel/sql-createpublication.html
Kind Regards,
Peter Smith.
Fujitsu Australia
