maria-developers team mailing list archive

[Sergei Golubchik <sergii@xxxxxxxxx>]

Hi, MARK!

On Dec 29, MARK CALLAGHAN wrote:
> On Mon, Dec 28, 2009 at 9:20 AM, Sergei Golubchik <sergii@xxxxxxxxx> wrote:
> >
> >  trn1> start transaction; insert t1 select * from t2;
> >  trn1> commit;
> >  trn1>> ... xa_prepare() ...
> 
> >  trn2> start transaction; insert t2 values (1); commit;
> >  trn2>> xa_prepare(); binlog.write(); xa_commit();
> >
> >  trn1> ... binlog.write(); xa_commit();
> >
> > and you have incorrect transaction order in binlog.
> 
> There are several issues here:
> * for SBR, tm1 cannot release row locks until it is guaranteed that it
> writes the binlog ahead of any dependent transactions. This is
> guaranteed by locking prepare_commit_mutex at the end of
> innobase_xa_prepare and not unlocking until row locks are released
> during the call to innobase_commit.

I don't see what prepare_commit_mutex has to do with it.  It is
guaranteed by row locks released at commit time, no matter whether
prepare_commit_mutex exists or not.
 
> * at least for the plugin the order in which InnoDB prepare is done
> might not match the order in which transactions are written to the
> binlog. InnoDB locks prepare_commit_mutex in innobase_xa_prepare after
> doing a prepare (the call to trx_prepare_for_mysql). It is unlocked
> after the commit record is written to the InnoDB transaction buffer
> and before that buffer is flushed to disk. What does match today is
> the order of transactions in the binlog and the commit records in the
> InnoDB transaction log.

Yes, and this is what prepare_commit_mutex is for.
 
Regards / Mit vielen Grüßen,
Sergei

-- 
   __  ___     ___ ____  __
  /  |/  /_ __/ __/ __ \/ /   Sergei Golubchik <serg@xxxxxxx>
 / /|_/ / // /\ \/ /_/ / /__  Principal Software Engineer/Server Architect
/_/  /_/\_, /___/\___\_\___/  Sun Microsystems GmbH, HRB München 161028
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