Hi, On Monday 04 March 2013, Aymeric Augustin wrote: > On 4 mars 2013, at 04:04, Shai Berger <[email protected]> wrote: > > you need to be sure that, in all these places, either reads don't > > really affect consequent writes, or some constraint holds that is > > equivalent to serializability -- otherwise, negative effect is possible. > > PostgreSQL and Oracle use the "repeatable read" isolation level by default. > They are immune to this problem, because a sequence of reads followed by a > write has the same semantics with a transaction under "read committed" and > without a transaction. > > MySQL uses "read committed" and SQLite uses "serializable". Users of these > databases may see a different behavior. > > I'm going to add this to the list of backwards incompatibilities: > https://github.com/aaugustin/django/commit/876fddb68dd6990e87b15e683c498e41 > f8921f14#L4R437 ("Using unsupported database features" isn't correct for > MySQL and SQLite right now.) >
I want to point out how ironic this whole issue turns out. First of all, it appears the bulk of users who may experience the subtle breakage discussed are users of MySql -- the database of choice for Aymeric's groups 1 & 2, the main declared target audience for the fix. On the other hand, it probably serves them right -- the choice of MySql is usually motivated by putting less focus on database-level integrity and more on other factors, such as single-threaded performance and ease of deployment. But considering this last disparaging comment, it's only MySql code that will be turned from correct to broken, because -- on this specific point -- it turns out MySql is, by default, stricter than the others about integrity. I am speechless, Shai. -- You received this message because you are subscribed to the Google Groups "Django developers" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/django-developers?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
