Re: Disallow UPDATE/DELETE on table with unpublished generated column as REPLICA IDENTITY

Thanks for providing the comments.

On Tue, 12 Nov 2024 at 12:52, Zhijie Hou (Fujitsu)
<houzj.fnst@fujitsu.com> wrote:
>
> On Friday, November 8, 2024 7:06 PM Shlok Kyal <shlok.kyal.oss@gmail.com> wrote:
> >
> > Hi Amit,
> >
> > On Thu, 7 Nov 2024 at 11:37, Amit Kapila <amit.kapila16@gmail.com> wrote:
> > >
> > > On Tue, Nov 5, 2024 at 12:53 PM Shlok Kyal <shlok.kyal.oss@gmail.com>
> > wrote:
> > > >
> > > > To avoid the issue, we can disallow UPDATE/DELETE on table with
> > > > unpublished generated column as REPLICA IDENTITY. I have attached a
> > > > patch for the same.
> > > >
> > >
> > > +CREATE PUBLICATION pub_gencol FOR TABLE testpub_gencol; UPDATE
> > > +testpub_gencol SET a = 100 WHERE a = 1;
> > > +ERROR:  cannot update table "testpub_gencol"
> > > +DETAIL:  Column list used by the publication does not cover the
> > > replica identity.
> > >
> > > This is not a correct ERROR message as the publication doesn't have
> > > any column list associated with it. You have added the code to detect
> > > this in the column list code path which I think is not required. BTW,
> > > you also need to consider the latest commit 7054186c4e for this. I
> > > guess you need to keep another flag in PublicationDesc to detect this
> > > and then give an appropriate ERROR.
> >
> > I have addressed the comments and provided an updated patch. Also, I am
> > currently working to fix this issue in back branches.
>
> Thanks for the patch. I am reviewing it and have some initial comments:
>
>
> 1.
> +                       char attgenerated = get_attgenerated(relid, attnum);
> +
>
> I think it's unnecessary to initialize attgenerated here because the value will
> be overwritten if pubviaroot is true anyway. Also, the get_attgenerated()
> is not cheap.
>
Fixed

> 2.
>
> I think the patch missed to check the case when table is marked REPLICA
> IDENTITY FULL, and generated column is not published:
>
> CREATE TABLE testpub_gencol (a INT, b INT GENERATED ALWAYS AS (a + 1) STORED NOT NULL);
> ALTER TABLE testpub_gencol REPLICA IDENTITY FULL;
> CREATE PUBLICATION pub_gencol FOR TABLE testpub_gencol;
> UPDATE testpub_gencol SET a = 2;
>
> I expected the UPDATE to fail in above case, but it can still pass after applying the patch.
>
Fixed

> 3.
>
> +                * If the publication is FOR ALL TABLES we can skip the validation.
> +                */
>
> This comment seems not clear to me, could you elaborate a bit more on this ?
>
I missed to handle the case FOR ALL TABLES. Have removed the comment.

> 4.
>
> Also, I think the patch does not handle the FOR ALL TABLE case correctly:
>
> 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 ALL TABLEs;
> UPDATE testpub_gencol SET a = 2;
>
> I expected the UPDATE to fail in above case as well.
>
Fixed

> 5.
>
> +       else if (cmd == CMD_UPDATE && !pubdesc.replident_has_valid_gen_cols)
> +               ereport(ERROR,
> +                               (errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
> +                                errmsg("cannot update table \"%s\"",
> +                                               RelationGetRelationName(rel)),
> +                                errdetail("REPLICA IDENTITY consists of an unpublished generated column.")));
>
> I think it would be better to use lower case "replica identity" to consistent
> with other existing messages.
>
Fixed

I have attached the updated patch here.

Thanks and Regards,
Shlok Kyal