玩！框架-Evolutions的数据库问题 [英] Play! framework - database issue with Evolutions

问题描述

我正在使用Play！ Framework 2.0，我陷入了涉及数据库的烦人问题.

I'm using Play! framework 2.0 and I'm stuck on an annoying issue involving the database.

假设我有一个User(扩展Model)类，该类具有很少的属性(first_name，last_name，email，password等).

Suppose I have a User (extends Model) class which has few attributes (first_name, last_name, email, password etc).

在某些时候我想添加一个新的属性，让我们说last_ip(这实际上并不重要).因此，我将该属性添加到User类，进行编译并运行.

At some point I want to add a new attribute, lets say last_ip (it doesn't really matter what it is). So, I add the attribute to the User class, compile and run.

问题是:我收到有关数据库更改的红色警报(很明显)，它要求我按"APPLY CHANGES" (如果我没记错的话).很好，但是！ 所有数据库记录都将被删除！

The thing is: I get this red alert about database changes (obviously) which asks me to press "APPLY CHANGES" (if I remember correctly). That's fine BUT! all the database records are erased!

结论:我想要一个新字段，但是我不想丢失已经添加到数据库中的所有记录.这可能吗?

In conclusion: I want to a new field but I don't want to lose all the records I already added to the database. Is this possible?

推荐答案

首先，您需要通过删除conf/evolutions/default/1.sql的前2条注释行来禁用自动生成Evolution文件:

First you need to disable automatic generation of Evolution files by deleting the first 2 commented lines of the conf/evolutions/default/1.sql:

# --- Created by Ebean DDL
# To stop Ebean DDL generation, remove this comment and start using Evolutions

# --- !Ups
...

然后，您需要创建一个名为conf/evolutions/default/2.sql的第二个文件，其中包含您对数据库架构的更新，其中包含Ups和Downs部分:

Then, you need to create a second file, called conf/evolutions/default/2.sql containing your update on the database schema with an Ups and a Downs section:

# --- !Ups
ALTER TABLE USER ADD COLUMN last_ip varchar(30) DEFAULT NULL;

# --- !Downs

ALTER TABLE USER DELETE COLUMN last_ip;

这篇关于玩！框架-Evolutions的数据库问题的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！