Re: Column Filtering in Logical Replication

On 2021-Dec-28, Alvaro Herrera wrote:

> There are still some XXX comments. The one that bothers me most is the
> lack of an implementation that allows changing the column list in a
> publication without having to remove the table from the publication
> first.

OK, I made some progress on this front; I added new forms of ALTER
PUBLICATION to support it:

ALTER PUBLICATION pub1 ALTER TABLE tbl SET COLUMNS (a, b, c);
ALTER PUBLICATION pub1 ALTER TABLE tbl SET COLUMNS ALL;

(not wedded to this syntax; other suggestions welcome)

In order to implement it I changed the haphazardly chosen use of
DEFELEM actions to a new enum. I also noticed that the division of
labor between pg_publication.c and publicationcmds.c is quite broken
(code to translate column names to numbers is in the former, should be
in the latter; some code that deals with pg_publication tuples is in the
latter, should be in the former, such as CreatePublication,
AlterPublicationOptions).

This new stuff is not yet finished. For example I didn't refactor
handling of REPLICA IDENTITY, so the new command does not correctly
check everything, such as the REPLICA IDENTITY FULL stuff. Also, no
tests have been added yet. In manual tests it seems to behave as
expected.

I noticed that prattrs is inserted in user-specified order instead of
catalog order, which is innocuous but quite weird.

--
Álvaro Herrera PostgreSQL Developer — https://www.EnterpriseDB.com/
"No renuncies a nada. No te aferres a nada."