liquibase-example

This project could be a used as

• a tutorial for learning the basics in liquibase
• a base for dicussing on how-to-use liquibase in a collaboration development project

This project is a simple example of a liquibase-project with maven ( http://www.liquibase.org/ ).
This liquibase-project is ready to run with MySQL and postgreSQL
Dependencies to mysql- and posrgresql-connectors are found in the maven pom.xml

By stating this is simple example : Not using complex commands, nor using extension

This simple project contains 5 changesets :

• 4 changesets that 'creates a table'
• 1 changeset that 'alters a table' by adding a column

#disucssion topic

In a project with multiple developers using a version control system (VCS)

###working as a team

• Guarantees that all the developers have the same schema on their local computer
  • how : by version controlling the changelog-files
• Every developer has a unique liquibase.properties-file (contains schema&credentials)
  • how : ignoring the liquibase.properties-file (if using git, update the .gitignore-file)

###updating the schema in a test-environment using a CI-tool

Check if you are able to update your database in your stage/test-enviroment with liquibase.

1. Create a liquibase-project as a module amongs your other projects.
2. version control the project.
3. CI-tool: Run this project as a build-step before the module that depends on the db. 1. obs : credentials are stored in the liquibase.properties-file

#prereq

Database

In this example the database is called 'denmark'.
You have to create the database before running the project

• see the liquibase.properties-file
  • setting: url=jdbc:mysql://localhost/denmark

Software:

• java
• maven
• a database-engine of choice

#important files for maven.

• pom.xml
  • db: mysql-connector-java (version '5.1.37')
  • db: postgresql (version '9.1-901-1.jdbc4')
  • liquibase: liquibase-maven-plugin

#Files for the liquibase-project.

Necessary files

• liquibase.properties
  • contains : driver and url to the database
  • contains : credentials
  • contains : path to the master.xml-file
  • contains : additional such as ; 'verbose = true', 'dropFirst = false'
• master.xml
  • contains : path to 'db.changelog-x.y.xml' , x.y are version-nr.
• db.changelog-1.0.xml
  • contains : all of your changesets (note : every changeset has to has a unique id)

You are able to have multiple 'db.changelog-x.y.xml'-files
This project contains 2 files ; db.changelog-1.0.xml and db.changelog-5.0.xml
In this example every file has its responsibility

• The db.changelog-1.0.xml contains all your changesets,
• The db.changelog-5.0.xml contains a reference to an .sql-file
  
  • The default-insert-for-admin_config.sql contains example content.

Other files

The following files are not necessary for the project.
They are just here as a configuration example.

• liquibase.mysql.properties
• liquibase.postgresql.properties

Writing changelogs in liquibase

In this example changesets are written in XML
You are not restrained to using XML for changesets.
Other formats are YAML, JSON and SQL
How-To-Documentation

Simple rules

• You create new changelogs in the changelog-file
• You do not delete old changelogs
• Every changelog has a unique id

#How to run the Liquibase-project To run the project
type 'mvn clean install' in the same directory that the pom.xml-file resides

Check your database
The following 5 tables should have been created

• 3 tables defined in the changelog-files
  • ADMIN_CONFIG
  • IMAGE
  • MEDIA
• Additional 2 liquibase-tables
  • DATABASECHANGELOG
  • DATABASECHANGELOGLOCK

Additional stuff

Creating db-documentation

command-line tool:

"Using change information stored in the change logs and an existing database, Liquibase can generate database change documentation " How-To-dbdoc

NOTE : 'javadoc'-style documenation is created with this tool

Going from a 'legacy'-database to a changeset-file.

command-line tool:

"When starting to use Liquibase on an existing database, it is often useful, particularly for testing, to have a way to generate the change log to create the current database schema. Liquibase allows you to do this with the “generateChangeLog” command_line command." How-To-Generate_changelogs

"Note that this command currently has some limitations. It does not export the following types of objects: Stored procedures, functions, packages,Triggers"