Evolving Agile Databases

Evolving Databases in Agile Umar Akhter & Rohith Rajagopal

Good DB Management Principles
Provide each developer with his/her own DB instance
This allows developers to try things out without affecting other developers
Sometimes a developer might want 2 instances - one for testing and another for development

Don't use binary db dumps
Because they are hard to version control/merge
Use scripts to create the DB schema
So a new dev can easily recreate the schema

Version control the scripts used to create/change the DB schema
To keep the DB schema in sync with the code which uses it
Automate running the scripts which create the schema
Because you will need to create the schema multiple times and you should automate repetitive tasks.
Use bat file or ant file

Use alter scripts rather than drop table and recreate (or hbm2ddl)
both drop table/recreate and hbm2ddl will delete existing data
Don't hardcode the paths while automating
It's easier to move across machines if the paths are in one place (property file, environment variables)

Make sure your tests are easily repeatable
You should be able to run your tests any number of times without manual intervention in between
Make your tests clean up after each run
Make sure your scripts are repeatable
You shouldn't need any manual steps to figure out which script to run to get your DB schema right
You should be able to invoke the same command which (irrespective of the current state of the DB) will upgrade you to the correct version of the schema

Use a tool like DB Deploy which
Keeps track of applied alter version in the DB
figures out from the schema + the alter files which alters to apply
Upgrading production databases becomes very easy
Reduced testing overhead for upgrade scripts
Deployment becomes easy and fast!!

Further Reading
http://martinfowler.com/articles/evodb.html
http://databaserefactoring.com/
http://goforthandcode.blogspot.com/2007/12/brief-history-of-database.html
http://goforthandcode.blogspot.com/2008/01/schema-to-survive-winds-of-change.html

Evolving Agile Databases

by Naresh Jain

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