Horton

Re: Skipping logical replication transactions on subscriber side

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, vignesh C <vignesh21@gmail.com>, Greg Nancarrow <gregn4422@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>
Date: 2021-12-02T06:48:17Z
Lists: pgsql-hackers 
On Wed, Dec 1, 2021 at 11:57 AM houzj.fnst@fujitsu.com
<houzj.fnst@fujitsu.com> wrote:
>
> On Wednesday, December 1, 2021 1:23 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> > Okay, I've attached an updated patch. Please review it.
> >
>
> I agreed that checking the result only once makes the test more stable.
> The patch looks good to me.
>

Pushed.

Now, coming back to the skip_xid patch. To summarize the discussion in
that regard so far, we have discussed various alternatives for the
syntax like:

a. ALTER SUBSCRIPTION ... [SET|RESET] SKIP TRANSACTION xxx;
b. Alter Subscription <sub_name> SET ( subscription_parameter [=value]
[, ... ] );
c. Alter Subscription <sub_name> On Error ( subscription_parameter
[=value] [, ... ] );
d. Alter Subscription <sub_name> SKIP ( subscription_parameter
[=value] [, ... ] );
where subscription_parameter can be one of:
xid = <xid_val>
lsn = <lsn_val>
...

We didn't prefer (a) as it can lead to more keywords as we add more
options; (b) as we want these new skip options to behave and be set
differently than existing subscription properties because of the
difference in their behavior; (c) as that sounds more like an action
to be performed on a future condition (error/conflict) whereas here we
already knew that an error has happened;

As per discussion till now, option (d) seems preferable.  In this, we
need to see how and what to allow as options. The simplest way for the
first version is to just allow one xid to be specified at a time which
would mean that specifying multiple xids should error out. We can also
additionally allow specifying operations like 'insert', 'update',
etc., and then relation list (list of oids). What that would mean is
that for a transaction we can allow which particular operations and
relations we want to skip.

I am not sure what exactly we can provide to users to allow skipping
initial table sync as we can't specify XID there. One option that
comes to mind is to allow specifying a combination of copy_data and
relid to skip table sync for a particular relation. We might think of
not doing anything for table sync workers but not sure if that is a
good option.

Thoughts?

-- 
With Regards,
Amit Kapila.

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