Django 迁移错误:您无法更改 M2M 字段或从 M2M 字段更改，或通过 = 在 M2M 字段上添加或删除 [英] Django migration error :you cannot alter to or from M2M fields, or add or remove through= on M2M fields

问题描述

我正在尝试将 M2M 字段修改为 ForeignKey 字段.命令 validate 显示没有问题，当我运行 syncdb 时:

I'm trying to modify a M2M field to a ForeignKey field. The command validate shows me no issues and when I run syncdb :

ValueError: Cannot alter field xxx into yyy they are not compatible types (you cannot alter to or from M2M fields, or add or remove through= on M2M fields)

所以我无法进行迁移.

class InstituteStaff(Person):
    user                 = models.OneToOneField(User, blank=True, null=True)
    investigation_area   = models.ManyToManyField(InvestigationArea, blank=True,)
    investigation_group  = models.ManyToManyField(InvestigationGroup, blank=True)
    council_group        = models.ForeignKey(CouncilGroup, null=True, blank=True)
    #profiles            = models.ManyToManyField(Profiles, null = True, blank = True)
    profiles             = models.ForeignKey(Profiles, null = True, blank = True)

这是我的第一个 Django 项目，欢迎提出任何建议.

This is my first Django project so any suggestions are welcome.

推荐答案

我偶然发现了这个，虽然我不太关心我的数据，但我仍然不想删除整个数据库.因此，我打开了迁移文件并将 AlterField() 命令更改为运行良好的 RemoveField() 和 AddField() 命令.我丢失了我在特定领域的数据，但没有别的.

I stumbled upon this and although I didn't care about my data much, I still didn't want to delete the whole DB. So I opened the migration file and changed the AlterField() command to a RemoveField() and an AddField() command that worked well. I lost my data on the specific field, but nothing else.

即

migrations.AlterField(
    model_name='player',
    name='teams',
    field=models.ManyToManyField(related_name='players', through='players.TeamPlayer', to='players.Team'),
),

到

migrations.RemoveField(
    model_name='player',
    name='teams',
),
migrations.AddField(
    model_name='player',
    name='teams',
    field=models.ManyToManyField(related_name='players', through='players.TeamPlayer', to='players.Team'),
),

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