Re: Disallow UPDATE/DELETE on table with unpublished generated column as REPLICA IDENTITY

On Sat, 16 Nov 2024 at 00:10, Shlok Kyal <shlok(dot)kyal(dot)oss(at)gmail(dot)com> wrote:
>
> Thanks for providing the comments. I have fixed all the comments and
> attached the updated patch.

Few comments:
1) The replident_has_valid_gen_cols flag is set when either an update
or delete operation is published by the publication.
+ /*
+ * Check if all columns which are part of the REPLICA
IDENTITY is
+ * published.
+ */
+ if (!pubform->pubgencols &&
+ (pubform->pubupdate || pubform->pubdelete) &&
+ replident_has_unpublished_gen_col(pubid,
relation, ancestors,
+
pubform->pubviaroot))
+ pubdesc->replident_has_valid_gen_cols = false;

You should create two separate flags—one for updates and one for
deletes—and set them accordingly, based on the operation being
published. This is similar to how the cols_valid_for_update and
cols_valid_for_delete flags are handled for column lists.

As shown in the test below, the delete operation fails even though the
delete operation is not published by the pub_gencol publication:
CREATE TABLE testpub_gencol (a INT, b INT GENERATED ALWAYS AS (a + 1)
STORED NOT NULL);
CREATE UNIQUE INDEX testpub_gencol_idx ON testpub_gencol (b);
ALTER TABLE testpub_gencol REPLICA IDENTITY USING index testpub_gencol_idx;

CREATE PUBLICATION pub_gencol FOR TABLE testpub_gencol with ( PUBLISH
= 'update');

-- This should be successful, since the publication is not publishing delete:
postgres=# delete from testpub_gencol ;
ERROR: cannot delete from table "testpub_gencol"
DETAIL: Replica identity consists of an unpublished generated column.

2) Since the code in replident_has_unpublished_gen_col and
pub_collist_contains_invalid_column is largely identical, we can
consolidate them into a single function that handles both column lists
and relation columns. The function name, header comments, and internal
comments should be updated accordingly.

Regards,
Vignesh