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

[Pavan D. <pav...@gm...>]

On Wed, Oct 9, 2013 at 11:49 AM, Koichi Suzuki <koi...@gm...>wrote:

> Hmm.. Yes, it could be serious.   I suppose that CTID changes only when
> vacuum full occurs.
>

CTID will also change every time a row is updated. So the bug should be
very easy to reproduce. One easiest way to compile different datanodes with
diferent block size. Another way could be to update/delete from a
replicated table and vacuum the table on one datanode but not other and
then again update several rows in the table. Most likely the new versions
on two different nodes will not have the same CTID anymore.


> Vacuum freeze will updates xmim to the smallest value and usual vacuum
> recycles "dead" row area.   We may have a chance to assign different CTIDs
> to the same rows in replicated table if vacuum full runs locally in
> datanodes.  (My assumption may be wrong.   Does vacuum freeze move tuples
> and change their CTID?)
>
>
No, it does not.

Thanks,
Pavan

-- 
Pavan Deolasee
http://www.linkedin.com/in/pavandeolasee