0

Work Environment:
1. Django 1.11
2. Python 3.6
3. MySQL Community Server- 5.7.21

I've been using django-jsonfield for my Django models.

import jsonfield
from django.db import models


class MySampleModel(models.Model):
    name = models.CharField(max_length=123)
    json_data = jsonfield.JSONField(default={})


As we knew, this particular field doesn't support JSON lookups and aggregation because it created as a LongText in MYSQL backend.

So, I decided to use Django-MYSQL, which support JSONField too, hence I changed my models.py as,

import jsonfield
from django.db import models
from django_mysql.models import JSONField as MYSQLJSONField


class MySampleModel(models.Model):
    name = models.CharField(max_length=123)
    json_data = jsonfield.JSONField(default={})
    new_jsonfield = MYSQLJSONField(default=dict)


then I ran makemigrations command and it succesfully excecuted and generated migration file.But, when try to run migrate, it throws the error, as

django.db.utils.OperationalError: (1101, "BLOB, TEXT, GEOMETRY or JSON column 'new_jsonfield' can't have a default value")


Traceback:

Running migrations:
  Rendering model states... DONE
  Applying spider.0055_run_new_jsonfield...Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/usr/local/lib/python3.6/site-packages/django/db/backends/mysql/base.py", line 112, in execute
    return self.cursor.execute(query, args)
  File "/usr/local/lib/python3.6/site-packages/MySQLdb/cursors.py", line 226, in execute
    self.errorhandler(self, exc, value)
  File "/usr/local/lib/python3.6/site-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
    raise errorvalue
  File "/usr/local/lib/python3.6/site-packages/MySQLdb/cursors.py", line 217, in execute
    res = self._query(query)
  File "/usr/local/lib/python3.6/site-packages/MySQLdb/cursors.py", line 378, in _query
    rowcount = self._do_query(q)
  File "/usr/local/lib/python3.6/site-packages/MySQLdb/cursors.py", line 341, in _do_query
    db.query(q)
  File "/usr/local/lib/python3.6/site-packages/MySQLdb/connections.py", line 280, in query
    _mysql.connection.query(self, query)
_mysql_exceptions.OperationalError: (1101, "BLOB, TEXT, GEOMETRY or JSON column 'new_jsonfield' can't have a default value")

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

Traceback (most recent call last):
  File "./manage.py", line 8, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/__init__.py", line 353, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python3.6/site-packages/django/core/management/__init__.py", line 345, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/base.py", line 348, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/base.py", line 399, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/commands/migrate.py", line 200, in handle
    executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python3.6/site-packages/django/db/migrations/executor.py", line 92, in migrate
    self._migrate_all_forwards(plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python3.6/site-packages/django/db/migrations/executor.py", line 121, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python3.6/site-packages/django/db/migrations/executor.py", line 198, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/usr/local/lib/python3.6/site-packages/django/db/migrations/migration.py", line 123, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/usr/local/lib/python3.6/site-packages/django/db/migrations/operations/fields.py", line 62, in database_forwards
    field,
  File "/usr/local/lib/python3.6/site-packages/django/db/backends/mysql/schema.py", line 50, in add_field
    super(DatabaseSchemaEditor, self).add_field(model, field)
  File "/usr/local/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 396, in add_field
    self.execute(sql, params)
  File "/usr/local/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 110, in execute
    cursor.execute(sql, params)
  File "/usr/local/lib/python3.6/site-packages/django/db/backends/utils.py", line 79, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/usr/local/lib/python3.6/site-packages/raven/contrib/django/client.py", line 123, in execute
    return real_execute(self, sql, params)
  File "/usr/local/lib/python3.6/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/usr/local/lib/python3.6/site-packages/django/db/utils.py", line 95, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/usr/local/lib/python3.6/site-packages/django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/usr/local/lib/python3.6/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/usr/local/lib/python3.6/site-packages/django/db/backends/mysql/base.py", line 112, in execute
    return self.cursor.execute(query, args)
  File "/usr/local/lib/python3.6/site-packages/MySQLdb/cursors.py", line 226, in execute
    self.errorhandler(self, exc, value)
  File "/usr/local/lib/python3.6/site-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
    raise errorvalue
  File "/usr/local/lib/python3.6/site-packages/MySQLdb/cursors.py", line 217, in execute
    res = self._query(query)
  File "/usr/local/lib/python3.6/site-packages/MySQLdb/cursors.py", line 378, in _query
    rowcount = self._do_query(q)
  File "/usr/local/lib/python3.6/site-packages/MySQLdb/cursors.py", line 341, in _do_query
    db.query(q)
  File "/usr/local/lib/python3.6/site-packages/MySQLdb/connections.py", line 280, in query
    _mysql.connection.query(self, query)
django.db.utils.OperationalError: (1101, "BLOB, TEXT, GEOMETRY or JSON column 'new_jsonfield' can't have a default value")


Generated Migration File

from __future__ import unicode_literals

from django.db import migrations
import django_mysql.models


class Migration(migrations.Migration):

    dependencies = [
        ('app_name', 'some_prev_migrationfile'),
    ]

    operations = [
        migrations.AddField(
            model_name='mysamplemodel',
            name='new_jsonfield',
            field=django_mysql.models.JSONField(default=dict),
        ),
    ]


Question

How can I safely migrate from django-jsonfield to Django-MYSQL at this context?

JPG
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  • Your error looks very similar to [this issue](https://github.com/adamchainz/django-mysql/issues/417), although the comments on that ticket suggest that it should be fixed in Django 1.11. – Alasdair Jun 12 '18 at 13:18

1 Answers1

0

This should work-

import jsonfield
from django.db import models
from django_mysql.models import JSONField as MYSQLJSONField


class MySampleModel(models.Model):
    name = models.CharField(max_length=123)
    json_data = jsonfield.JSONField(default={})
    new_jsonfield = MYSQLJSONField(default={})

Or try:

import jsonfield
from django.db import models
from django_mysql.models import JSONField as MYSQLJSONField

def default_json():
    return {'data': 'bar'}

class MySampleModel(models.Model):
    name = models.CharField(max_length=123)
    json_data = jsonfield.JSONField(default={})
    new_jsonfield = MYSQLJSONField(default=default_json)

Hope this helps :)

V.Khakhil
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  • Got error, **(django_mysql.E017) Do not use mutable defaults for JSONField HINT: Mutable defaults get shared between all instances of the field, which probably isn't what you want. You should replace your default with a callable, e.g. replace default={} with default=dict. The default you passed was '{}'** – JPG Jun 12 '18 at 13:08
  • have a look https://django-mysql.readthedocs.io/en/latest/model_fields/json_field.html – V.Khakhil Jun 12 '18 at 13:09
  • json_data = jsonfield.JSONField(default={}), I think this is working for you. Don't you use same for both column ?? – V.Khakhil Jun 12 '18 at 13:12
  • I tried to call `callable function` for `default`. But, it shows the same error as I mentioned in `Question` – JPG Jun 12 '18 at 13:12
  • As I said in OP, the `jsonfield` doesn't support [json-lookups](https://django-mysql.readthedocs.io/en/latest/model_fields/json_field.html#exact-lookups) – JPG Jun 12 '18 at 13:13
  • try to set default=None – V.Khakhil Jun 12 '18 at 13:14