Re: row filtering for logical replication

On Mon, Dec 13, 2021 at 8:49 PM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:
>
> PSA the v46* patch set.
>

0001

(1)

"If a subscriber is a pre-15 version, the initial table
synchronization won't use row filters even if they are defined in the
publisher."

Won't this lead to data inconsistencies or errors that otherwise
wouldn't happen? Should such subscriptions be allowed?

(2) In the 0001 patch comment, the term "publication filter" is used
in one place, and in others "row filter" or "row-filter".

src/backend/catalog/pg_publication.c
(3) GetTransformedWhereClause() is missing a function comment.

(4)
The following comment seems incomplete:

+ /* Fix up collation information */
+ whereclause = GetTransformedWhereClause(pstate, pri, true);

src/backend/parser/parse_relation.c
(5)
wording? consistent?
Shouldn't it be "publication WHERE expression" for consistency?

+ errmsg("publication row-filter WHERE invalid reference to table \"%s\"",
+ relation->relname),

src/backend/replication/logical/tablesync.c
(6)

(i) Improve wording:

BEFORE:
/*
* Get information about remote relation in similar fashion the RELATION
- * message provides during replication.
+ * message provides during replication. This function also returns the relation
+ * qualifications to be used in COPY command.
*/

AFTER:
/*
- * Get information about remote relation in similar fashion the RELATION
- * message provides during replication.
+ * Get information about a remote relation, in a similar fashion to
how the RELATION
+ * message provides information during replication. This function
also returns the relation
+ * qualifications to be used in the COPY command.
*/

(ii) fetch_remote_table_info() doesn't currently account for ALL
TABLES and ALL TABLES IN SCHEMA.

src/backend/replication/pgoutput/pgoutput.c
(7) pgoutput_tow_filter()
I think that the "ExecDropSingleTupleTableSlot(entry->scantuple);" is
not needed in pgoutput_tow_filter() - I don't think it can be non-NULL
when entry->exprstate_valid is false

(8) I am a little unsure about this "combine filters on copy
(irrespective of pubaction)" functionality. What if a filter is
specified and the only pubaction is DELETE?

0002

src/backend/catalog/pg_publication.c
(1) rowfilter_walker()
One of the errdetail messages doesn't begin with an uppercase letter:

+ errdetail_msg = _("user-defined types are not allowed");

src/backend/executor/execReplication.c
(2) CheckCmdReplicaIdentity()

Strictly speaking, the following:

+ if (invalid_rfcolnum)

should be:

+ if (invalid_rfcolnum != InvalidAttrNumber)

0003

src/backend/replication/logical/tablesync.c
(1)
Column name in comment should be "puballtables" not "puballtable":

+ * If any publication has puballtable true then all row-filtering is

(2) pgoutput_row_filter_init()

There should be a space before the final "*/" (so the asterisks align).
Also, should say "... treated the same".

/*
+ * If the publication is FOR ALL TABLES then it is treated same as if this
+ * table has no filters (even if for some other publication it does).
+ */

Regards,
Greg Nancarrow
Fujitsu Australia