[django]让 BigIntegerField 字段自增长

默认的 id 字段是 IntegerField 属性,长度是 11。

现在要将它改为 BigIntegerField 属性,因为它的长度是更长。

class Foo(models.Model):
    id = models.BigIntegerField(primary_key=True)
    #...

更改后的数据库字段信息:

mysql> desc foo_bar;
+--------------+------------+------+-----+---------+-------+
| Field        | Type       | Null | Key | Default | Extra |
+--------------+------------+------+-----+---------+-------+
| id           | bigint(20) | NO   | PRI | NULL    |       |

问题出来了,更改后的 id 没有自增长的功能。

解决办法就是自定义一个字段属性:

代码结构:

foo   # app
|-fields.py
|-models.py

代码:

# fields.py
from django.db.models import fields
from south.modelsinspector import add_introspection_rules


class BigIntegerAutoField(fields.BigIntegerField):
    def db_type(self, connection):
        if 'mysql' in connection.__class__.__module__:
            return 'bigint AUTO_INCREMENT'
        return super(BigIntegerAutoField, self).db_type(connection)

add_introspection_rules([], ["^foo\.fields\.BigIntegerAutoField"])


# models.py
from .fields import BigIntegerAutoField


class Bar(models.Model):
    id = BigIntegerAutoField(primary_key=True)
    # ...

结果:

mysql> desc foo_bar;
+--------------+------------+------+-----+---------+----------------+
| Field        | Type       | Null | Key | Default | Extra          |
+--------------+------------+------+-----+---------+----------------+
| id           | bigint(20) | NO   | PRI | NULL    | auto_increment |

参考

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