DatabaseError:值太长，无法更改类型字符（20）

Question

解决方案：-我删除了导致此问题的migration.py文件。用相同的代码创建一个新的应用程序现在可以工作了

我不知道为什么我会得到一个变化（20）的错误，即使我已经设置了最大长度为200的CharField 我查看了所有其他帖子，所有帖子都对值的长度有疑问。 但是，即使我在名称字段中输入“abc”，也会出现此错误。感谢您的帮助。谢谢

Django版本：3.1.5 Python版本：3.8.5

from django.db import models
from django.contrib.gis.db import models
from django.db.models import Manager as GeoManager

# Create your models here.
class Incidences(models.Model):
    name = models.CharField(max_length=200)
    location = models.PointField(srid=4326)
    objects = GeoManager()
    
    def _str_(self):
        return self.name

Traceback (most recent call last):
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\db\backends\utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)

The above exception (value too long for type character varying(20)
) was the direct cause of the following exception:
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\core\handlers\exception.py", line 47, in inner
    response = get_response(request)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\core\handlers\base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\contrib\admin\options.py", line 614, in wrapper
    return self.admin_site.admin_view(view)(*args, **kwargs)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\utils\decorators.py", line 130, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\views\decorators\cache.py", line 44, in _wrapped_view_func
    response = view_func(request, *args, **kwargs)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\contrib\admin\sites.py", line 233, in inner
    return view(request, *args, **kwargs)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\contrib\admin\options.py", line 1653, in add_view
    return self.changeform_view(request, None, form_url, extra_context)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\utils\decorators.py", line 43, in _wrapper
    return bound_method(*args, **kwargs)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\utils\decorators.py", line 130, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\contrib\admin\options.py", line 1534, in changeform_view
    return self._changeform_view(request, object_id, form_url, extra_context)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\contrib\admin\options.py", line 1580, in _changeform_view
    self.save_model(request, new_object, form, not add)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\contrib\admin\options.py", line 1093, in save_model
    obj.save()
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\db\models\base.py", line 753, in save
    self.save_base(using=using, force_insert=force_insert,
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\db\models\base.py", line 790, in save_base
    updated = self._save_table(
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\db\models\base.py", line 895, in _save_table
    results = self._do_insert(cls._base_manager, using, fields, returning_fields, raw)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\db\models\base.py", line 933, in _do_insert
    return manager._insert(
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\db\models\manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\db\models\query.py", line 1254, in _insert
    return query.get_compiler(using=using).execute_sql(returning_fields)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\db\models\sql\compiler.py", line 1397, in execute_sql
    cursor.execute(sql, params)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\db\backends\utils.py", line 98, in execute
    return super().execute(sql, params)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\db\backends\utils.py", line 66, in execute
    return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\db\backends\utils.py", line 75, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\db\backends\utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\db\utils.py", line 90, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "C:\Users\anuj\geo_django_tutorial\tutorial_geodjango\lifeingis\lib\site-packages\django\db\backends\utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)

Exception Type: DataError at /admin/reporter/incidences/add/
Exception Value: value too long for type character varying(20)