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: Greg Nancarrow <gregn4422@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.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>
Date: 2021-10-18T01:33:21Z
Lists: pgsql-hackers 
On Tue, Oct 12, 2021 at 7:58 PM Greg Nancarrow <gregn4422@gmail.com> wrote:
>
> On Tue, Oct 12, 2021 at 4:00 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> >
> > I've attached updated patches.
> >
>
> Some comments for the v16-0003 patch:

Thank you for the comments!

>
> (1) doc/src/sgml/logical-replication.sgml
>
> The output from "SELECT * FROM pg_stat_subscription_errors;" still
> shows "last_failed_time" instead of "last_error_time".

Fixed.

>
> doc/src/sgml/ref/alter_subscription.sgml
> (2)
>
> Suggested update (and fix typo: restrited -> restricted):
>
> BEFORE:
> +          Setting and resetting of <literal>skip_xid</literal> option is
> +          restrited to superusers.
> AFTER:
> +          The setting and resetting of the
> <literal>skip_xid</literal> option is
> +          restricted to superusers.

Fixed.

>
> (3)
> Suggested improvement to the wording:
>
> BEFORE:
> +          incoming change or by skipping the whole transaction.  This option
> +          specifies transaction ID that logical replication worker skips to
> +          apply.  The logical replication worker skips all data modification
> AFTER:
> +          incoming changes or by skipping the whole transaction.  This option
> +          specifies the ID of the transaction whose application is to
> be skipped
> +          by the logical replication worker. The logical replication worker
> +          skips all data modification

Updated.

>
> (4) src/backend/replication/logical/worker.c
>
> Suggested improvement to the comment wording:
>
> BEFORE:
> + * Stop the skipping transaction if enabled. Otherwise, commit the changes
> AFTER:
> + * Stop skipping the transaction changes, if enabled. Otherwise,
> commit the changes

Fixed.

>
>
> (5) skip_xid value validation
>
> The validation of the specified skip_xid XID value isn't great.
> For example, the following value are accepted:
>
>     ALTER SUBSCRIPTION sub SET (skip_xid='123abcz');
>     ALTER SUBSCRIPTION sub SET (skip_xid='99$@*');

Hmm, this is probably a problem of xid data type. For example, we can do like:

postgres(1:12686)=# select 'aa123'::xid;
 xid
-----
   0
(1 row)

postgres(1:12686)=# select '123aa'::xid;
 xid
-----
 123
(1 row)

It seems a problem to me. Perhaps we can fix it in a separate patch.
What do you think?

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