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
