[Dovecot] Quota transaction bug?

[Jasper Bryant-Greene]

On Tue, Jul 24, 2007 at 02:46:11PM -0700, David Jonas wrote:
> Jasper Bryant-Greene wrote:
> > On Tue, Jul 24, 2007 at 02:09:23PM -0700, David Jonas wrote:
> >> < SELECT current FROM quota WHERE ...
> >>> 513965019
> >> < BEGIN
> >> < INSERT INTO quota (current, ...
> >> < COMMIT
> >>> ??  (error_r appears to be (null))
> > 
> > Unrelated to the original post, but the above would appear to be a bug to me.
> > 
> > Because the SELECT is done before the transaction starts, the value in the
> > INSERT which is based on the SELECT may no longer be consistent with the
> > actual value in that table.
> 
> I don't think it uses the value. The INSERT statement that comes next
> does an UPDATE if the key exists. The value represented as 0 here is the
> change in quota value:
> 
> INSERT INTO quota (current, path, username) VALUES (0, 'quota/storage',
> 'user at example.com') ON DUPLICATE KEY UPDATE current = current + 0;
> 
> So it's only added to or inserted, never changed then replaced.

OK, so absolutely nothing about the INSERT (including whether or not it is
performed) depends on anything about the result from the SELECT?

Jasper