Re: [HACKERS] Restrict concurrent update/delete with UPDATE of partition key

On Fri, Feb 2, 2018 at 2:11 PM, amul sul <sulamul(at)gmail(dot)com> wrote:
> On Fri, Jan 26, 2018 at 11:58 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> [....]
>> I think you can manually (via debugger) hit this by using
>> PUBLICATION/SUBSCRIPTION syntax for logical replication. I think what
>> you need to do is in node-1, create a partitioned table and subscribe
>> it on node-2. Now, perform an Update on node-1, then stop the logical
>> replication worker before it calls heap_lock_tuple. Now, in node-2,
>> update the same row such that it moves the row. Now, continue the
>> logical replication worker. I think it should hit your new code, if
>> not then we need to think of some other way.
>>
>
> I am able to hit the change log using above steps. Thanks a lot for the
> step by step guide, I really needed that.
>
> One strange behavior I found in the logical replication which is reproducible
> without attached patch as well -- when I have updated on node2 by keeping
> breakpoint before the heap_lock_tuple call in replication worker, I can see
> a duplicate row was inserted on the node2, see this:
>
..
>
> I am thinking to report this in a separate thread, but not sure if
> this is already known behaviour or not.
>

I think it is worth to discuss this behavior in a separate thread.
However, if possible, try to reproduce it without partitioning and
then report it.

>
> Updated patch attached -- correct changes in execReplication.c.
>

Your changes look correct to me.

I wonder what will be the behavior of this patch with
wal_consistency_checking [1]. I think it will generate a failure as
there is nothing in WAL to replay it. Can you once try it? If we see
a failure with wal consistency checker, then we need to think whether
(a) we want to deal with it by logging this information, or (b) do we
want to mask it or (c) something else?

[1] - https://www.postgresql.org/docs/devel/static/runtime-config-developer.html

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com