Re: Disallow UPDATE/DELETE on table with unpublished generated column as REPLICA IDENTITY

Thanks for providing the comments.

On Thu, 14 Nov 2024 at 12:22, vignesh C <vignesh21(at)gmail(dot)com> wrote:
>
> On Wed, 13 Nov 2024 at 11:15, Shlok Kyal <shlok(dot)kyal(dot)oss(at)gmail(dot)com> wrote:
> >
> > Thanks for providing the comments.
> >
> > On Tue, 12 Nov 2024 at 12:52, Zhijie Hou (Fujitsu)
> > <houzj(dot)fnst(at)fujitsu(dot)com> wrote:
> > >
> > > On Friday, November 8, 2024 7:06 PM Shlok Kyal <shlok(dot)kyal(dot)oss(at)gmail(dot)com> wrote:
> > > >
> > > > Hi Amit,
> > > >
> > > > On Thu, 7 Nov 2024 at 11:37, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > > > >
> > > > > On Tue, Nov 5, 2024 at 12:53 PM Shlok Kyal <shlok(dot)kyal(dot)oss(at)gmail(dot)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 unpublished generated column as REPLICA IDENTITY.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.
>
> Few comments:
> 1) In the first check relation->rd_rel->relispartition also is checked
> whereas in the below it is not checked, shouldn't the same check be
> there below to avoid few of the function calls which are not required:
> + if (pubviaroot && relation->rd_rel->relispartition)
> + {
> + publish_as_relid =
> GetTopMostAncestorInPublication(pubid, ancestors, NULL);
> +
> + if (!OidIsValid(publish_as_relid))
> + publish_as_relid = relid;
> + }
> +
>
> + if (pubviaroot)
> + {
> + /* attribute name in the child table */
> + char *colname =
> get_attname(relid, attnum, false);
> +
> + /*
> + * Determine the attnum for the
> attribute name in parent (we
> + * are using the column list defined
> on the parent).
> + */
> + attnum = get_attnum(publish_as_relid, colname);
> + attgenerated =
> get_attgenerated(publish_as_relid, attnum);
> + }
> + else
> + attgenerated = get_attgenerated(relid, attnum);
I have updated the if condititon

> 2) I think we could use check_and_fetch_column_list to see that it is
> not a column list publication instead of below code:
> + if (!puballtables)
> + {
> + tuple = SearchSysCache2(PUBLICATIONRELMAP,
> +
> ObjectIdGetDatum(publish_as_relid),
> +
> ObjectIdGetDatum(pubid));
> +
> + if (!HeapTupleIsValid(tuple))
> + return false;
> +
> + (void) SysCacheGetAttr(PUBLICATIONRELMAP, tuple,
> +
> Anum_pg_publication_rel_prattrs,
> + &isnull);
> +
> + ReleaseSysCache(tuple);
> + }
> +
> + if(puballtables || isnull)

Yes we can use it. I have updated the patch.

> 3) Since there is only a single statement, remove the enclosing parenthisis:
> + if (!pubform->pubgencols &&
> + (pubform->pubupdate || pubform->pubdelete) &&
> + replident_has_unpublished_gen_col(pubid,
> relation, ancestors,
> +
> pubform->pubviaroot, pubform->puballtables))
> + {
> + pubdesc->replident_has_valid_gen_cols = false;
> + }
>
Fixed

> 4) Pgindent should be run there are few issues:
> 4.a)
> +extern bool replident_has_unpublished_gen_col(Oid pubid, Relation relation,
> +
> List *ancestors, bool pubviaroot, bool
> puballtables);
> 4.b)
> + }
> +
> + if(puballtables || isnull)
> + {
> + int x;
> + Bitmapset *idattrs = NULL;
> 4.c)
> + * generated column we should error out.
> + */
> + if(relation->rd_rel->relreplident == REPLICA_IDENTITY_FULL &&
> + relation->rd_att->constr &&
> relation->rd_att->constr->has_generated_stored)
> + result = true;
> 4.d)
> + while ((x = bms_next_member(idattrs, x)) >= 0)
> + {
> + AttrNumber attnum = (x +
> FirstLowInvalidHeapAttributeNumber);
> + char attgenerated;
>
Fixed

> 5) You could do this in a single line comment:
> + /*
> + * Check if any REPLICA IDENTITY column is an generated column.
> + */
> + while ((x = bms_next_member(idattrs, x)) >= 0)
>

Fixed

> 6) I felt one of update or delete is enough in this case as the code
> path is same:
> +UPDATE testpub_gencol SET a = 100 WHERE a = 1;
> +DELETE FROM testpub_gencol WHERE a = 100;
> +
> +-- error - generated column "b" is not published and REPLICA IDENTITY
> is set FULL
> +ALTER TABLE testpub_gencol REPLICA IDENTITY FULL;
> +UPDATE testpub_gencol SET a = 100 WHERE a = 1;
> +DELETE FROM testpub_gencol WHERE a = 100;
> +DROP PUBLICATION pub_gencol;
> +
> +-- ok - generated column "b" is published and is part of REPLICA IDENTITY
> +CREATE PUBLICATION pub_gencol FOR TABLE testpub_gencol with
> (publish_generated_columns = true);
> +UPDATE testpub_gencol SET a = 100 WHERE a = 1;
> +DELETE FROM testpub_gencol WHERE a = 100;

Removed the 'DELETE' case.

I have addressed the comments and updated the patch.

Thanks and Regards,
Shlok Kyal