[Cosmo-dev] new migration framework

[Randy Letness]

In order to do a Derby migration, I pretty much had to write java code, 
so I ended up writing a basic database migration framework that works 
with both Derby and MySQL.  I have checked this in under 
cosmo/migration.  Instructions on building and running are contained in 
the README.txt.

The basics:

1. build using 'mvn package', which creates an all-in-one jar under 
cosmo/migration/target
2. edit migration.properties file located in cosmo/migration to suit 
your database (both Derby and MySQL examples are included)
3. run the executable jar file like: java -jar 
target/cosmo-migration-jar-with-dependencies.jar migration.properties
    or for verbose mode: java -jar 
cosmo-migration-jar-with-dependencies.jar -v migration.properties

The nice thing about this framework is that it can be configured to 
migrate any previous version of Cosmo (starting with 0.5) to the latest 
version, by choosing what migrations to run (based on the version found 
in the database) and running them in order. This will make implementing 
migrations for future version of Cosmo simple.   It can be as easy as 
dropping in a sql script and configuring a spring bean, or if the 
migration requires complex data manipulation, you can implement a 
migrateData() method using JDBC.  On my machine the JDBC based migration 
against MySQL is faster than the sql script that uses cursors.  That 
could be because I'm not an expert in writing stored procedures and the 
current script is highly inefficient.

So now that there are two ways of migrating a MySQL db, do we support 
both?  Do we need both?  The difference is that the new migration 
framework requires java to be run, but since Cosmo is a java program, I 
don't see that as too big of a problem.  Right now its not a big deal , 
but down the road when someone wants to migrate from 0.6 to 0.7, its 
nice to only have to run a single command, instead of running a script 
to migrate 0.6 to 0.6.1, then another for 0.6.1 to 0.6.2, and finally 
from 0.6.2 to 0.7.0.

We can also hook this framework up to the DbListenter and do 
auto-migrations on Cosmo startup if we wanted to.

-Randy