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Re: Patch for MDEV-12874 - UPDATE statements with the same source and target
Here is a version that reuses used logic when one searches and updates the same index.
The principal impact is that we can't use the can_compare optimization because we have to store all new values for all keys of tempfile.
But this correct a bug in my previous implementation (on update through a view).
This simplifies the code a bit, but not much (no needs of tempfile_key).
I don't see how to do this more simpler.
If you have better ideas, I listen your suggestions.
Thank you very much.
> -----Message d'origine-----
> De : Sergei Golubchik [mailto:serg@xxxxxxxxxxx]
> Envoyé : vendredi 18 août 2017 01:24
> À : jerome brauge
> Cc : maria-developers@xxxxxxxxxxxxxxxxxxx; Alexander Barkov
> Objet : Re: Patch for MDEV-12874 - UPDATE statements with the same
> source and target
> Hi, jerome!
> On Jul 21, jerome brauge wrote:
> > Hello,
> > Here is a patch for MDEV-12874 (on branch 10.2-ext).
> > Can anyone review it ?
> I'll send comments about the code later, don't want to mix small details and
> the big question. So, the big one:
> Why did you introduce completely new code for handling updates with the
> same table? mysql_update has logic when one searches and updates the
> same index (UPDATE idx=idx*2 WHERE idx > 5). That's used_key_is_modified
> variable. I'd thought you could reuse that. You might still need your
> tempfile_newdata, but even then it'll be much less code and simpler
> implementation. Would that work?
> Chief Architect MariaDB
> and security@xxxxxxxxxxx