This document discusses evolutionary database design and tools for managing database changes. It begins with background on planned vs evolutionary development approaches. The author then describes their experience with database projects at PRIA and HireRight that highlighted challenges with managing changes across multiple databases. Finally, the document evaluates tools for database change management like Ruby migrations, RedGate SQL Compare, MySQL Workbench, Oracle Enterprise Manager, DBDeploy, and LiquiBase, concluding that LiquiBase provides the most options while working with any RDBMS.

1. July 1, 2009
Evolutionary
database design
DevClub.eu,
30.06.2009
Andrei Solntsev

2. Agenda
 begin
» background
» my experience
» tools
 end;

3. begin
процесс разработки программного обеспечения
Плановый («водопад») Эволюционный
На раннем этапе • Допускать изменения
• выявить требования, на всех стадиях
• согласовать, • Но управлять изменениями
• спроектировать,
• согласовать
и затем приступить к кодированию
принципиальная позиция –
минимизация изменений за счет максимально упростить
обширной предварительной работы. возможность изменений

4. @author Martin Fowler
1999: Refactoring: Improving
the Design of Existing Code
http://www.amazon.com/exec/obidos/ASIN/0201485672
2000: Continuous Integration
http://www.martinfowler.com/articles/continuousIntegration.html
2003: Evolutionary Database Design
http://www.martinfowler.com/articles/evodb.html

5. @compare
Рефакторинг базы данных сложнее, чем рефакторинг кода
• Сохранение информационной семантики
• Миграция данных
• В отличие от обычного ПО, невозможно просто
удалить старый код и заменить новым.
• большое количество связей
• период поддержки устаревшего кода

6. <img src=“book.pdf”/>

7. @experience
My experience
 PRIA
 HireRight
 HireRight 2.0 ?

8. PRIA
Single DB environment
Developers Product Manager Salespeople
Production
Production
Testers
Users
Deployment is not a problem 

9. Multi-DB environment
Developer #1 Tester #1
Salespeople Production
Users
Demo Production
Developer #2 Tester #2
Deployment becomes a problem 

10. HireRight: deployment
CVS DB
ALTER TABLE man ADD
COLUMN length
Create index man_idx
CREATE INDEX Installation
women_id_idx scripts
DROP TABLE raha
CREATE TABLE money (
eek NUMBER
Problems:
); • scripts reinstallation
• DB recreation
ALTER TABLE money ADD CONS • DB synchronization

11. Database Change Management
An automated process is needed to make the process of
upgrading out-of-date databases simple
 We need a Database Change Management tool.
My findings:
Ruby migrations - http://www.oracle.com/technology/pub/articles/kern-rails-migrations.html
RedGate SQL compare - http://www.red-gate.com/products/SQL_Compare/index.htm
MySQL Workbench – Diff & Synchronization
http://dev.mysql.com/tech-resources/articles/workbench_database_management.html
Oracle Enterprise Manager (change management pack)
DB Deploy - http://dbdeploy.com/
LiquiBase - http://www.liquibase.org/

12. Apache DDL Utils
http://db.apache.org/ddlutils/
<database name="testdb">
<table name="author">
<column name="author_id" type="INTEGER"
primaryKey="true" required="true"/>
<column name="name" type="VARCHAR"
size="50" required="true"/>
<column name="organisation" type="VARCHAR"
size="50" required="false"/>
</table>
<index name="book_isbn">
<index-column name="isbn"/>
</index>
</database>
Based on XML, automatically generates SQL scripts to update DB.

13. Incremental Schema Changes
 All database schemas can be thought of as a compilation of
incremental changes made over time to accommodate new
functionality
 As updates are applied to a database, the changes will be
recorded in a table similar to the following:
Change Date
1_Create_Customer_Table.sql 4-15-07
2_Add_e-mail_address_column.sql 4-17-07
3_Add_fax_number_column.sql 4-18-07
4_Add_transaction_table.sql 4-21-07
5_Add_transaction_status_column.sql 4-24-07
6_Add_customer-transaction_view.sql 4-27-07

14. DBDeploy ThoughWorks.com
1. Go to directory with SQL files:
• “1 create_customer_table.sql”
• “2 add_customer_id_constraint.sql”
• …
• Run “ant”
Output:
[dbdeploy] dbdeploy 3.0-SNAPSHOT
[dbdeploy] Reading change scripts from directory
/tmp/dbdeploy/dbdeploy-3.0-SNAPSHOT/example...
[dbdeploy] Changes currently applied to database:
[dbdeploy] (none)
[dbdeploy] Scripts available:
[dbdeploy] 1, 2
[dbdeploy] To be applied:
[dbdeploy] 1, 2
[dbdeploy] Generating undo scripts...
[sql] Executing resource:
/tmp/dbdeploy/dbdeploy-3.0-SNAPSHOT/example/output.sql
[sql] 7 of 7 SQL statements executed successfully

15. DBDeploy options
• Naming convention for delta scripts:
NUMBER COMMENT.SQL
• Re-execution – NOT POSSIBLE
• Undo section – marked by comments:
CREATE TABLE FOO (
FOO_ID INTEGER NOT NULL, FOO_VALUE VARCHAR(30) );
ALTER TABLE FOO ADD CONSTRAINT PK_FOO PRIMARY KEY (FOO_ID);
--//@UNDO
DROP TABLE FOO;
http://dbdeploy.com/documentation/getting-started/rules-for-using-dbdeploy/

16. LiquiBase LiquiBase.org
The main XML describing all delta scripts:
<databaseChangeLog>
<changeSet id="1" author="bob">
<createTable tableName="department">
<column name="id" type="int">
<constraints primaryKey="true" nullable="false"/>
</column>
<column name="name" type="varchar(50)">
<constraints nullable="false"/>
</column>
<column name="active" type="boolean" defaultValue="1"/>
</createTable>
</changeSet>
</databaseChangeLog>

17. LiquiBase
Run:
liquibase --driver=com.mysql.jdbc.Driver
--classpath=/path/to/classes
--changeLogFile=com/example/db.changelog.xml
--url="jdbc:mysql://localhost/example"
--username=user
--password=asdf
migrate
Also possible to run:
• Ant script
• Maven plugin
• Built-in java code
• Spring
• Grails
• Servlet Listener

18. LiquiBase options
• Custom order of scripts (user-defined)
• Re-execution – POSSIBLE (with attributes)

19. LiquiBase options
And many other options:
• DBMS
• SQL checksum
• context
• long transaction
• pre-conditions

20. Outcome
My findings:
RedGate SQL compare 1. commercial
MySQL Workbench – Diff & Synchronization 2. RDBMS-specific
3. but probably good
Oracle Enterprise Manager
Ruby migrations - Seems to be cool, need to try
- Written on Ruby
DB Deploy - Written by authoritative people
- Simple
- Convection over configuration
Written
LiquiBase - More configuration than DBDeploy on
- More options than DBDeploy Java
- Works with any RDBMS
- Eclipse plugin

21. end;
Links:
http://www.refactoring.com/ - Code refactoring (1999)
http://databaserefactoring.com/ - DB refactoring (2003)
Books:
Рефакторинг баз данных: эволюционное проектирование.
http://www.williamspublishing.com/Books/978-5-8459-1157-5.html