MySQL Opaque Features

In the practice of MySQL Support Engineers the trickiest problem of an application is not a crash or something absolutely bad, but wrong logic in tackling a problem. Sometimes, a problem looks simple, but developers could spend several hours to find what is wrong and why. Some of such problems with MySQL occur because of some misunderstanding of MySQL behavior. We’ll present some of the most interesting cases.

Every problem would be examined with its components::

1. Description of the problem
2. Code showing the problem
3. Additional explanation what is wrong.
4. Solution
5. Explanation why MySQL behaves in such a way and why it is good.
6. Additional reading if needed.

We will show cases affecting different parts of MySQL server, touching several difficult areas of using MySQL features in the wrong way.

Practice shows some MySQL features are more difficult to understand than others. For such features we will show more than one example.

You will know

1. Why you have to wait execution of query referenced to non-existent column instead of getting error immediately
2. Why “Illegal mix of collations” error and other character set problems occur
3. Why LAST_INSERT_ID does not return inserted ID
4. Why application does not report several errors while reports other
5. More

All our examples come from real cases. Fortunately the Support practics provides lots of such examples. Of course, some of them have been polished on purpose to hide private data or to make the case more clear or to show additional examples of MySQL usage. But every single problem has really occurred in the practice of MySQL Support engineers.

At the end of the presentation we will provide several tips on how to find what is wrong in user application. Especially for complicated features.