如何使用Sugar Orm升级数据库? [英] How to upgrade database with Sugar Orm?

问题描述

我有一个简单的实体:

public class MyEntity extends SugarRecord {

    String name;
    int    value;

    public MyEntity() {
        //empty ctr for sugar orm
    }

    public MyEntity(String name, int value) {
        this.name = name;
        this.value = value;
    }
}

在App启动时，我创建一个实例并保存如下:

On App start I make an instance and save it like this:

  Log.i("db_test", "count_before: "+MyEntity.count(MyEntity.class)+"");
  new MyEntity("name", 10).save();
  Log.i("db_test", "count_after: "+MyEntity.count(MyEntity.class)+"");

在日志中，我可以看到:

In the log I can see:

04-12 14:58:52.538: I/db_test(10691): count_before: 0
04-12 14:58:52.555: I/Sugar(10691): MyEntity saved : 1
04-12 14:58:52.555: I/db_test(10691): count_after: 1

运行良好.

那么，如果我决定要向MyEntity类添加属性，该怎么办?像这样:

So what if I decide I would like to add a property to MyEntity class. like this:

public class MyEntity extends SugarRecord {

    String name;
    int    value;
    int    anotherValue; ///< A new property.
//...

此后，由于模型已更改，因此我增加了Databse版本. 因此，我将清单中的以下字段从1增加到2.

After this I increment the Databse version because the model has changed. So I increase the following field in the manifest from 1 to 2.

  <meta-data
   android:name="VERSION"
   android:value="2"/>

这一次，当我运行我的应用程序时，出现以下错误:

This time when i ran my app I got the following error:

E/SQLiteLog(11125): (1) table MY_ENTITY has no column named ANOTHER_VALUE

java.lang.RuntimeException: Unable to start activity ComponentInfo{...}: 

android.database.sqlite.SQLiteException: table MY_ENTITY has no column named ANOTHER_VALUE (code 1): , while compiling: INSERT OR REPLACE  INTO MY_ENTITY(ANOTHER_VALUE,ID,VALUE,NAME) VALUES (?,?,?,?)

那为什么会这样呢?

我已经在Java对象上设置了此属性.

I have made this property on my Java object.

我已经增加了数据库版本.

I have incremented the database version.

我做错了什么

推荐答案

虽然这不是理想的解决方案，但使用升级文件手动更改表应该可以使插入/替换工作.

Whilst it's not an ideal solution, using an upgrade file to manually alter the table should allow the insert / replace to work.

AFAIK，VERSION值仅用于标识是否应运行补丁.

AFAIK, the VERSION value is only used to identify if patches should be run.

在您的情况下，可能是在您的assets/sugar_upgrades/文件夹中添加了一个名为"2.sql"的文件，其中包含:

In your case, it would be a case of adding a file called "2.sql" into your assets/sugar_upgrades/ folder, containing:

ALTER TABLE my_entity ADD COLUMN another_value int;

来源: SugarORM

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