Re: [Postgres-xc-developers] [postgres-xc:bugs] #454 Update triggers on replicated tables may corrupt data

[Amit K. <ami...@en...>]

http://sourceforge.net/p/postgres-xc/bugs/402/

But this issue has nothing do with triggers. I think there should be some
way to reproduce without triggers. Although, if any user triggers or unique
constraint triggers makes our job of reproducing the issue easy, that would
be good.


On 27 September 2013 09:33, Ashutosh Bapat
<ash...@en...>wrote:

> Hi Hackers,
> While working on triggers me and Amit had thought of this problem and
> there should be a mail from Amit in that regards. What stopped us from
> working on this more, was a reproduction scenario where same row landed on
> two different nodes with different CTID. We couldn't get that scenario even
> with complex ingredients like vacuum analyze etc. If you are hitting this
> problem, can one provide us a reproduction.
>
>
> On Thu, Sep 26, 2013 at 11:30 PM, mason_s <ma...@us...> wrote:
>
>> ------------------------------
>>
>> * [bugs:#454] <http://sourceforge.net/p/postgres-xc/bugs/454/> Update
>> triggers on replicated tables may corrupt data*
>>
>> *Status:* open
>> *Created:* Thu Sep 26, 2013 06:00 PM UTC by mason_s
>> *Last Updated:* Thu Sep 26, 2013 06:00 PM UTC
>> *Owner:* nobody
>>
>> We noticed that when updating a single row on a replicated table that we
>> were getting duplicate key violations, even though the primary key columns
>> were not involved.
>>
>> We dug deeper and noticed that the mechanism uses ctid to identify what
>> to update for update triggers that are non-"shippable" and executed on a
>> coordinator. In the case of a replicated table, the ctid value may be
>> different on different nodes for each tuple. It appears that Postgres-XC
>> just uses one ctid value from one of the nodes and then sends down the same
>> UPDATE statement to all of the individual nodes.
>>
>> It should either get each ctid for each node and update, or determine the
>> corresponding unique key values and use that in the generated WHERE clause.
>> ------------------------------
>>
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>
>
>
> --
> Best Wishes,
> Ashutosh Bapat
> EnterpriseDB Corporation
> The Postgres Database Company
>
>
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