如何将我的models.TextField改为models.JSONField？

Question

我使用django作为我的后端，它运行得很好，但是在我尝试替换text = models.TextField(blank=True, null=True) text = models.JSONField(blank=True, null=True)之后，文本字段显示为带有斜杠的字符串\

"text": "{\"name\": [\"test\", \"test2\"]}", json字段看起来像json

        "style": {
            "borderRadius": "5px",
            "backgroundColor": "orange"
        },

尽管他们俩都是约翰逊菲尔德。

models.py

class elements(models.Model):
    tag = models.CharField(blank=True, null=True, max_length=20)

# it was # text = models.TextField(blank=True, null=True)
# now it is 
text = models.JSONField(blank=True, null=True)

    src = models.TextField(blank=True, null=True)

    style = models.JSONField(blank=True, null=True)

    main = models.ForeignKey(
        'self', null=True, blank=True, related_name="sub", on_delete=models.PROTECT)

    def __str__(self):
        return "<elements: {} {}>".format(self.tag, self.text, self.src, self.style)

    def __repr__(self):
        return self.__str__()

在运行python manage.py makemigrations之后，python manage.py migrate也得到了一个错误

DETAIL:  Token "add" is invalid.
CONTEXT:  JSON data, line 1: add...

the full error

Operations to perform:
  Apply all migrations: account, admin, auth, authtoken, contenttypes, myapp, sessions, sites
Running migrations:
  Applying myapp.0006_auto_20200905_1410...Traceback (most recent call last):
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
psycopg2.errors.InvalidTextRepresentation: invalid input syntax for type json
DETAIL:  Token "add" is invalid.
CONTEXT:  JSON data, line 1: add...


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    main()
  File "manage.py", line 18, in main
    execute_from_command_line(sys.argv)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/core/management/__init__.py", line 401, in execute_from_command_line
    utility.execute()
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/core/management/__init__.py", line 395, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/core/management/base.py", line 330, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/core/management/base.py", line 371, in execute
    output = self.handle(*args, **options)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/core/management/base.py", line 85, in wrapped
    res = handle_func(*args, **kwargs)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/core/management/commands/migrate.py", line 245, in handle
    fake_initial=fake_initial,
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/migrations/executor.py", line 117, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/migrations/executor.py", line 147, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/migrations/executor.py", line 227, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/migrations/migration.py", line 124, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/migrations/operations/fields.py", line 236, in database_forwards
    schema_editor.alter_field(from_model, from_field, to_field)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/backends/base/schema.py", line 572, in alter_field
    old_db_params, new_db_params, strict)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/backends/postgresql/schema.py", line 168, in _alter_field
    new_db_params, strict,
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/backends/base/schema.py", line 726, in _alter_field
    params,
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/backends/base/schema.py", line 142, in execute
    cursor.execute(sql, params)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/backends/utils.py", line 98, in execute
    return super().execute(sql, params)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/backends/utils.py", line 66, in execute
    return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/backends/utils.py", line 75, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/utils.py", line 90, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/Users/apple/Desktop/learning web stack from clonning notion.so/backend/env/lib/python3.7/site-packages/django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
django.db.utils.DataError: invalid input syntax for type json
DETAIL:  Token "add" is invalid.
CONTEXT:  JSON data, line 1: add...

• 注意:我尝试删除我的数据并重新迁移，但是没有工作。
• 注意:我使用的是postgreSQL

Answer 1

为了将文本字段转换为JSON，可以使用类似于以下内容的4步策略：

• 在模型中创建一个新的JSON列
• 使用--empty添加新迁移，并使用RunPython运行python函数，该函数选择整个模型，加载旧值，使用json.loads将其转换为JSON对象，并将其保存在新列中
• 删除旧的文本字段列
• 将较新的列重命名为原始列名。