Question: We all have our favourite database. If you look objectively at your chosen database, what drawbacks does it have and what could be improved?

The rules:

* One reply per drawback with;
* a short description of the limitation, followed by;
* a more detailed description, an explanation of how it could be done better or an example of another technology that does not have the same limitation.
* Do not diss any database that you haven't used extensively. It is easy to take potshots at other technologies but we want to learn form your experience, not your prejudice.

Answer: 
**Database** MySQL 5.0.x and above

**Defect** Ring replication errors lead to inconsistent data on different nodes

**Description**

The most serious problem in production we face at the moment is that in a MySQL ring the ring itself produces an error and stops replicating.

Building a ring (or Master-Master-replication) is possible since 5.x.x: You chain the databases in a "ring" so that the replicate data to each other. Every database-node gets all the changes from all other nodes.

We assume that the error lies behind autoincrement- failures. This is known from normal replication, too, but in the new version there are no sufficinet error messages in the error log. I highly recommend not to use this feature in MySQL as long as the problems here are not fixed.
PostgreSQL doesn't have a good failover solution, but I understand they're working on it.