Horton

Re: Skipping logical replication transactions on subscriber side

Masahiko Sawada <sawada.mshk@gmail.com>

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From: Masahiko Sawada <sawada.mshk@gmail.com>
To: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, "tanghy.fnst@fujitsu.com" <tanghy.fnst@fujitsu.com>, "osumi.takamichi@fujitsu.com" <osumi.takamichi@fujitsu.com>, Alexey Lesovsky <lesovsky@gmail.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Greg Nancarrow <gregn4422@gmail.com>
Date: 2021-09-21T04:53:01Z
Lists: pgsql-hackers

Attachments

Sorry for the late reply. I was on vacation.

On Tue, Sep 14, 2021 at 11:27 AM houzj.fnst@fujitsu.com
<houzj.fnst@fujitsu.com> wrote:
>
> From Thur, Sep 9, 2021 10:33 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> > Sorry for the late response. I've attached the updated patches that incorporate
> > all comments unless I missed something. Please review them.
>
> Thanks for the new version patches.
> Here are some comments for the v13-0001 patch.

Thank you for the comments!

>
> 1)
>
> +                                       pgstat_setheader(&errmsg.m_hdr, PGSTAT_MTYPE_SUBSCRIPTIONERRPURGE);
> +                                       pgstat_send(&errmsg, len);
> +                                       errmsg.m_nentries = 0;
> +                               }
>
> It seems we can invoke pgstat_setheader once before the loop like the
> following:
>
> +                       errmsg.m_nentries = 0;
> +                       errmsg.m_subid = subent->subid;
> +                       pgstat_setheader(&errmsg.m_hdr, PGSTAT_MTYPE_SUBSCRIPTIONERRPURGE);
>
> 2)
> +                                       pgstat_setheader(&submsg.m_hdr, PGSTAT_MTYPE_SUBSCRIPTIONPURGE);
> +                                       pgstat_send(&submsg, len);
>
> Same as 1), we can invoke pgstat_setheader once before the loop like:
> +               submsg.m_nentries = 0;
> +               pgstat_setheader(&submsg.m_hdr, PGSTAT_MTYPE_SUBSCRIPTIONPURGE);
>

But if we do that, we set the header even if there is no message to
send, right? Looking at other similar code in pgstat_vacuum_stat(), we
set the header just before sending the message. So I'd like to leave
them since it's cleaner.

>
> 3)
>
> +/* ----------
> + * PgStat_MsgSubscriptionErrPurge      Sent by the autovacuum to purge the subscription
> + *                                                                     errors.
>
> The comments said it's sent by autovacuum, would the manual vacuum also send
> this message ?

Right. Fixed.

>
>
> 4)
> +
> +       pgstat_send(&msg, offsetof(PgStat_MsgSubscriptionErr, m_reset) + sizeof(bool));
> +}
>
> Does it look cleaner that we use the offset of m_relid here like the following ?
>
> pgstat_send(&msg, offsetof(PgStat_MsgSubscriptionErr, m_relid));

Thank you for the suggestion. After more thought, it was a bit odd to
use PgStat_MsgSubscriptionErr to both report and reset the stats by
sending the part or the full struct. So in the latest version, I've
added a new message struct type to reset the subscription error
statistics.

I've attached the updated version patches. Please review them.

Regards,

-- 
Masahiko Sawada
EDB:  https://www.enterprisedb.com/

Commits

  1. Test ALIGNOF_DOUBLE==4 compatibility under ALIGNOF_DOUBLE==8.

  2. Reorder subskiplsn in pg_subscription to avoid alignment issues.

  3. Add ALTER SUBSCRIPTION ... SKIP.

  4. Optionally disable subscriptions on error.

  5. Update docs of logical replication for commit 8d74fc96db.

  6. Respect permissions within logical replication.

  7. Fix regression test failure caused by commit 8d74fc96db.

  8. Add a view to show the stats of subscription workers.

  9. Add logical change details to logical replication worker errcontext.

  10. Rename LOGICAL_REP_MSG_STREAM_END to LOGICAL_REP_MSG_STREAM_STOP.

  11. Fix typo in protocol.sgml.

  12. Remove unused argument in apply_handle_commit_internal().

  13. Fix replication of in-progress transactions in tablesync worker.

  14. Reorder pg_sequence columns to avoid alignment issue