Re: Proposal: Conflict log history table for Logical Replication

On Wed, 3 Dec 2025 at 16:57, Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>
> On Wed, Dec 3, 2025 at 9:49 AM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
> > >
> > > relid | 16391
> > > schemaname | public
> > > relname | conf_tab
> > > conflict_type | multiple_unique_conflicts
> > > remote_xid | 761
> > > remote_commit_lsn | 0/01761400
> > > remote_commit_ts | 2025-12-02 15:02:07.045935+00
> > > remote_origin | pg_16406
> > > key_tuple |
> > > remote_tuple | {"a":2,"b":3,"c":4}
> > > local_conflicts |
> > > {"{\"xid\":\"773\",\"commit_ts\":\"2025-12-02T15:02:00.640253+00:00\",\"origin\":\"\",\"tuple\":{\"a\":2,\"b\":2,\"c\":2}}","{\"xid\":\"
> > > 773\",\"commit_ts\":\"2025-12-02T15:02:00.640253+00:00\",\"origin\":\"\",\"tuple\":{\"a\":3,\"b\":3,\"c\":3}}","{\"xid\":\"773\",\"commit_ts\":\"2025-12-02T
> > > 15:02:00.640253+00:00\",\"origin\":\"\",\"tuple\":{\"a\":4,\"b\":4,\"c\":4}}"}
> > >
> >
> > Thanks, it looks good. For the benefit of others, could you include a
> > brief note, perhaps in the commit message for now, describing how to
> > access or read this array column? We can remove it later.
>
> Thanks, okay, temporarily I have added in a commit message how we can
> fetch the data from the JSON array field. In next version I will add
> a test to get the conflict stored in conflict log history table and
> fetch from it.

Few comments:
1) Currently pg_dump is not dumping conflict_log_table option, I felt
it should be included while dumping.

2) Is there a way to unset the conflict log table after we create the
subscription with conflict_log_table option

3) Any reason why this table should not be allowed to add to a publication:
+ /* Can't be conflict log table */
+ if (IsConflictLogTable(RelationGetRelid(targetrel)))
+ ereport(ERROR,
+ (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ errmsg("cannot add relation \"%s.%s\"
to publication",
+
get_namespace_name(RelationGetNamespace(targetrel)),
+
RelationGetRelationName(targetrel)),
+ errdetail("This operation is not
supported for conflict log tables.")));

Is the reason like the same table can be a conflict table in the
subscriber and prevent corruption in the subscriber

4) I did not find any documentation for this feature, can we include
documentation in create_subscription.sgml, alter_subscription.sgml and
logical_replication.sgml

Regards,
Vignesh