From: Michael Dykman
Date: September 17 2007 9:56pm
Subject: Re: Rollback on a Transaction with No Updates
List-Archive: http://lists.mysql.com/mysql/209152
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If your transaction are only 1 query deep, why use them at all?  An
individual query is already atomic, regardless of table type/server
mode.

 - michael dkyman


On 9/17/07, Robert DiFalco <rdifalco@stripped> wrote:
> While it is functionally equivalent I wonder if it the code paths taken
> are the same. I suppose for both commit and rollback mysql would have to
> look for any pending work, if there were none both would do nothing.
> That's what makes me think that there is probably no performance
> difference between the two. I ask this because my programmers like to do
> this:
>
>         con = ...
>         try
>         {
>            queryOnlyWith( con );
>         }
>         finally
>         {
>            con.rollback();
>         }
>
> And I wanted to make sure that this would perform the same and act the
> same as issuing a commit (unless there was an exception but I'm not
> analyzing that case).
>
> -----Original Message-----
> From: Baron Schwartz [mailto:baron@stripped]
> Sent: Monday, September 17, 2007 2:36 PM
> To: Robert DiFalco
> Cc: mysql@stripped
> Subject: Re: Rollback on a Transaction with No Updates
>
> Robert DiFalco wrote:
> > Is there any difference between calling rollback or commit on a
> > transaction that did not alter data? For example, not a read-only
> > transaction but a transaction that only performed read-only selects.
> > Any difference in performance between calling rollback or commit? I
> > know they are functionally the same at the high level.
>
> The only thing I could think of was possibly rollback would leave open
> transaction and its read view if you are running in REPEATABLE READ
> isolation mode, whereas commit begins a new transaction and discards the
> read view.  But I just tested that, and both commands start a new
> transaction and discard the read view.
>
> That's a long way of saying they are functionally equivalent as far as I
> know, as long as there are no changes to discard.
>
> Baron
>
>
>
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>


-- 
 - michael dykman
 - mdykman@stripped

 - All models are wrong.  Some models are useful.