.NET Migration工具
Migration是一种分布环境下的数据库同步工具,出现在Ruby on Rail框架里,MigratorDotNet是一个.NET类似于Ruby on Rail的Migrations的数据库版本系统。支持的数据库有MySQL (5.0, 5.1) ,PostgreSQL ,SQLite ,SQL Server (2000, 2005),Oracle (没有经过很好测试),可以通过NantTask,MSBuildTarget, Console Application三种方式来使用。
Migrations的类是Migration的子类,Migration主要有两个方法:Up方法定义这个版本该做什么,Down定义怎么回滚版本.
每一个Migration都应该是数据库中一个非常小的增量修改,常用的尺寸是创建一个表和给表增加一个字段或者多个字段,修改表的数据和对表执行一个ExecuteQuery自定义查询。保持Migration的尽量小,这样方便在版本之间的迁移,就在版本控制系统SVN,TFS那样,Migration的例子是这样的:
// Version 1
[Migration(1)]
public class CreateUserTable : Migration
{
public void Up()
{
Database.CreateTable("User",
new Column("UserId", DBType.Int32, ColumnProperties.PrimaryKeyWithIdentity),
new Column("Username", DBType.AnsiString, 25)
);
}
public void Down()
{
Database.RemoveTable("User");
}
}
Migration属性使用一个整数来表示,代表当前的数据库版本,工具就是通过这个属性来决定数据库之间的迁移。你如果使用控制台程序,版本号作为参数传给控制台程序,当然你也可以使用NAnt脚本或者MSBuild脚本。
下面是一段NAnt编译脚本:
<?xml version="1.0" ?>
<project default="migrate">
<property name="project.dir" value="."/>
<property name="output.dir" value="${project.dir}\Output" />
<loadtasks assembly="${project.dir}\lib\migrator\Migrator.NAnt.dll" />
<target name="clean" description="Deletes the previously built directories">
<delete dir="${output.dir}" failonerror="false" />
</target>
<target name="build" description="Builds Migration Project" depends="clean">
<msbuild project="${project.dir}\src\Migrations.Project\Migrations.Project.csproj">
<property name="Configuration" value="Debug" />
<property name="OutDir" value="${output.dir}\\" />
</msbuild>
</target>
<!-- Database Migrations task -->
<target name="migrate" description="Migrate the database" depends="build">
<!-- Using a version of -1 will cause the migration to migrate to the latest version -->
<property name="version" value="-1" overwrite="false" />
<migrate
provider="MySql"
connectionstring="Database=mydb;Data Source=localhost;User Id=mysqluser;Password=mysqlpassword;"
migrations="${output.dir}\Migrations.Project.dll"
to="${version}" />
</target>
</project>
如何写Migrate可以参看WritingMigrations。另外提一下SubSonic 2.1 RC1版本也增加Migrate功能,具体参看SubSonic: Using Migrations
数据库移植参考资料:
http://api.rubyonrails.com/classes/ActiveRecord/Migration.html
http://wiki.rubyonrails.org/rails/pages/UnderstandingMigrations
http://wiki.rubyonrails.org/rails/pages/UsingMigrations
Getting Started with Migrator.NET
http://www.lostechies.com/blogs/sean_chambers/archive/2008/06/04/getting-started-with-migrator-net-and-database-refactorings.aspx
(outdated) http://macournoyer.wordpress.com/2006/09/20/database-migration-for-net
Where did Migrator.NET come from
http://macournoyer.wordpress.com/2007/09/18/the-migrations-for-net-project-is-not-dead-yet
Migrator.NET Good Practices
http://macournoyer.wordpress.com/2007/02/11/agile-database-fun-with-the-migrator
Migrate NAnt Task
http://macournoyer.wordpress.com/2006/10/15/migrate-nant-task
Database Migrations for .NET
http://www.zorched.net/2008/04/20/database-migrations-for-net/
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