MYSQL-AND-TRANSACTIONAL-DDL.TXT

WARNING TO MYSQL USERS
----------------------

If you are using this library with MySQL, beware of the following
caveat!

Unlike PostgreSQL and SQLite, MySQL does not support transactional
Data Definition Language (DDL) statements such as CREATE TABLE. Since
dbmigrations is designed around the assumption that it's useful and
important to make migrations atomic, and since most migrations will have
at least some DDL in them, this means that dbmigrations cannot make
atomicity guarantees about your migrations if you are using MySQL as
your backend.  The MySQL docs have this to say:

http://dev.mysql.com/doc/refman/5.7/en/cannot-roll-back.html

This means that features like moo's "--test" flag will not do what you
expect, that mistakes in migrations will be tough to fix in development,
and that a problem in a migration in a production deployment COULD
HOSE YOUR DATABASE and BREAK RUNNING APPLICATIONS. Note that MySQL's
DDL statements cause an implicit commit, so any errors after each DDL
statement will have to be corrected by hand!

It is the author's opinion that this makes MySQL unfit for production
use and that you should strongly consider using some other backend such
as PostgreSQL which has much more robust support for transactional DDL.

You might be wondering why support for MySQL is included if it can be
so dangerous to use. Some users have requested and contributed support
for it, and of course we can't always choose to use a different backend
for preexisting systems. In those cases at least dbmigrations doesn't
make your problem any worse than it already is, provided you heed this
disclaimer. :)

You have been warned!