Thread

RE: Orphaned records in pg_replication_origin_status after subscription drop

Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com> — 2025-12-22T10:15:30Z

On Monday, December 22, 2025 2:09 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> On Mon, Dec 22, 2025 at 10:16 AM Zhijie Hou (Fujitsu)
> <houzj.fnst@fujitsu.com> wrote:
> >
> > On Monday, December 22, 2025 7:01 AM Michael Paquier
> <michael@paquier.xyz> wrote:
> > > On Sat, Dec 20, 2025 at 02:55:15PM +0530, Amit Kapila wrote:
> > > > As of today, I can't think of a case where next time (restart
> > > > after
> > > > error) we won't generate the same origin_name but I think this
> > > > will add the dependency that each time the origin name should be
> > > > generated the same.
> > >
> > > ReplicationOriginNameForLogicalRep() would generate the origin name
> > > as pg_suboid_relid, so we would always reuse the same origin name on
> > > restart as long as the subscription is not recreated, wouldn't we?
> > >
> > > > Also, moving just repl_origin_create part (leaving other things
> > > > like origin_advance at its location) would need some explanation
> > > > in comments which is that it has some dependency on
> > > > DropSubscription and cleanup. Anyway, if we want to go with
> > > > creating origin in a separate transaction than COPY, then we
> > > > should change few comments like: "It is possible that the origin
> > > > is not yet created for tablesync worker, this can happen for the
> > > > states before SUBREL_STATE_FINISHEDCOPY." in the code.
> > >
> > > Hmm.  So...  Do you think that it should be OK to just create a new
> > > transaction before we open the transaction that locks
> > > MyLogicalRepWorker->relid (one that opens a BEGIN READ ONLY on the
> > > remote side)?  And I guess that we would just move the
> > > replorigin_by_name(),
> > > replorigin_create() and ERROR into this new transaction?  Setting up
> > > replorigin_session_setup() and replorigin_session_origin could then
> > > be delayed until we have done the
> > > replorigin_advance() in BEGIN READ ONLY transaction?  By that I mean
> > > to leave the replorigin_advance() position untouched.  I have
> > > studied this code quite a bit.  I "think" that something among these
> > > lines would work, but I am not 100% sure if things are OK based the
> > > relstate we store in each of these phases.  If you have an argument that
> invalidates these lines, please feel free!
> >
> > I think the solution you outlined works. One nitpick is that, instead
> > of starting a new transaction, we could create the origin within the
> > same transaction that updates the DATASYNC states, thereby ensuring
> > the origin information is available as soon as the catalog is updated.
> > I think the bug won't happen as long as the origin is created in a
> > transaction separate from the one setting up the shared memory state.
> >
> 
> Agreed. But please update the comment (/* Update the state and make it
> visible to others. */) just before that transaction to reflect that origin will also
> be created in this transaction.

Updated.

> 
> > Additionally, if we relocate the origin creation code, we need to
> > remove the ERROR report. This is because the origin may already exist
> > if a table sync restarts due to an ERROR during the initial COPY. This
> > should be safe since the origin is created with the reserved name
> > "pg_xx," preventing users from creating another origin with the same name.
> >
> 
> Right.
> 
> + /*
> + * Advance the origin to the LSN got from walrcv_create_slot. This is
> + WAL
> + * logged for the purpose of recovery. Locks are to prevent the
> + * replication origin from vanishing while advancing.
> + */
> + LockRelationOid(ReplicationOriginRelationId, RowExclusiveLock);
> + replorigin_advance(originid, *origin_startpos, InvalidXLogRecPtr,
> +    true /* go backward */ , true /* WAL log */ );
> + UnlockRelationOid(ReplicationOriginRelationId, RowExclusiveLock);
> +
>   /*
>   * Setup replication origin tracking. The purpose of doing this before the
>   * copy is to avoid doing the copy again due to any error in setting up
>   * origin tracking.
>   */
> 
> Shouldn't the second comment starting from "Setup replication origin .." be
> merged with the previous one because it is also intended for the previous
> code change?

Agreed and merged.

Here is the V2 patch which addressed above comments.

Best Regards,
Hou zj