maria-developers team mailing list archive

[Arjen Lentz <arjen@xxxxxxxxxxxxx>]

Hi Philip

On 07/07/2010, at 5:21 PM, Philip Stoev wrote:
> What do you mean by "can be tricky and more often than not causes  
> hassles",

"Crashed" and inaccessible tables.

> and in general, what is the semantics of a DDL KILL operation? For  
> example, are you allowed to leave temporary files and if not, who is  
> responsible for cleaning them up -- the engine or the server?

See Stewart's answer - engine is responsible for all that.

> I am afraid that a timing-based method can only be used to test a  
> KILL during the main phase of the DDL, that is, when the temporary  
> table or the new index are being built. However, it would not be  
> possible to reliably hit any of the other phases, such as when the  
> old table is being replaced by the new table, without some explicit  
> instrumentation of the code.

Sure - but I think it's the main phase... user starting an ALTER  
TABLE, realising it's going to take a long time (forgot to set a large  
myisam_sort_buffer_size on a MyISAM table, for instance) and wants to  
abort, fix up the settings and try again (or wait until a more  
appropriate time later).

Cheers,
Arjen.


> ----- Original Message ----- From: "Arjen Lentz" <arjen@xxxxxxxxxxxxx>
> To: "maria-developers" <maria-developers@xxxxxxxxxxxxxxxxxxx>
> Cc: "Philip Stoev" <philip@xxxxxxxxx>
> Sent: Wednesday, July 07, 2010 3:03 AM
> Subject: How MySQL/MariaDB handles aborted DDL
>
>
> > Hi Philip, all
> >
> > Philip's bug on recovery from a kill -9 during DML reminded me...  
> > from  my experience, aborting a DDL query (ALTER TABLE - things  
> > like adding  an index usually) b.
> > By abort in this case I mean killing the connection/thread that  
> > does  the DDL.
> >
> > It would be great to somehow have a few test cases in the suite and  
> > it needs to be tested with all storage engines.
> > Provided the table it operates on is big enough, it should be  
> > possible  to just zap it by timing.
> > Thoughts?
> >
> > Cheers,
> > Arjen.

--
Arjen Lentz, Exec.Director @ Open Query (http://openquery.com)
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