how-to-create-migration-scripts.md

How to create migration scripts

How to create model in the database

First integrate Darwin to your project and create create.sql SQL script in a platform specific folder. Let's have new component adam with initial version 1.0:

1. Create initial setup script

Create a file on your classpath /META-INF/adam/sql/mysql/create.sql with example content:

create table ADAM (
	id integer not null auto_increment,
	preciousContent varchar(255) not null,
	constraint CNPK_ADAM primary key (id)
) engine=InnoDB;

2. Make it live with Darwin

Create Darwin bean in your Spring configuration:

@Configuration
@Import(DarwinConfiguration.class)
public class YourNameOfConfigFile {

    @Bean
    public Darwin adamSchema(ApplicationContext applicationContext) {
        return new DarwinBuilder(applicationContext, "adam", "1.0")              
                .withResourcePath("classpath:/META-INF/adam/sql/")
                .build();
    }

}

... and you're done - Darwin creates ADAM table for you once Spring tries to instantiate adamSchema bean. If you require ADAM table to exist in order to be used in other bean setup you should force Darwin bean to instantiate first using Spring DependsOn annotation.

How to upgrade existing model in database

1. Create patch script

Create a file on your classpath /META-INF/adam/sql/mysql/patch_1.1.sql with example content:

alter table ADAM add column additionalContent varchar(64) null;

2. Make it live with Darwin

Update version in your Darwin bean declaration in your Spring configuration:

@Configuration
@Import(DarwinConfiguration.class)
public class YourNameOfConfigFile {

    @Bean
    public Darwin adamSchema(ApplicationContext applicationContext) {
        return new DarwinBuilder(applicationContext, "adam", "1.1")              
                .withResourcePath("classpath:/META-INF/adam/sql/")
                .build();
    }

}

... and you're done - once Darwin bean is instantiated again, it finds out, that version of the model is 1.1, but there is older version (1.0) in the database and it automatically finds and applies patch_1.1.sql script. When it's finished it writes down that database now contains model with version 1.1.