South将DateField迁移到IntegerField [英] South migrate DateField to IntegerField

问题描述

我想改变我的模型

class Source(models.Model):
    release_date = models.DateField()

到

class Source(models.Model):
    release_date = models.IntegerField()

如预期的那样，我收到一个错误

as expected, I get an error

django.db.utils.DataError: (1264, "Out of range value for column 'release_date' at row 1")

我实际想要的是只保存一年在 IntegerField ，因为这是我需要的。有一个非常聪明的方式来采取现有的日期年份字段，并通过更改方法将其迁移到新的IntegerField

What I actually want is, to only save the year in the IntegerField as that is all I need. Is there a very intelligent way to take existing dates' year field and migrate it to the new IntegerField by altering the method

def forwards(self, orm):

如果没有，我可以改变字段类型而不会松动所有数据，丢失存储的日期，将是我支付的价格。

If not, how at all can I change the fieldtype without loosing all data, loosing the stored dates, would be a price i'd pay.

推荐答案

一个选项是将任务分解为3个迁移：

One option is to split the task into 3 migrations:

• 模式迁移：添加 release_year field


• 数据迁移：从 release_date 字段填写 release_year 字段


• 模式迁移：删除 release_date 字段并重命名 release_year 至 release_date

• schema migration: adding release_year field
• data migration: filling release_year field from release_date field
• schema migration: remove release_date field and rename release_year to release_date

模式迁移将被南部自动抓住（使用 sch emamigration --auto ），但您需要手动编写数据迁移，以下是您的 forward（）方法应如下所示：

Schema migrations would be caught by south automagically (using schemamigration --auto), but you need to write a data migration manually, here's how your forwards() method should look like:

def forwards(self, orm):
    for source in orm.Source.objects.all():
        source.release_year = source.release_date.year
        source.save()

希望有帮助。

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