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I'm trying to create a model with Geospatial field. When I try to migrate I receive the following error:

 Apply all migrations: admin, auth, contenttypes, map, sessions Running migrations: Applying map.0008_territorio_geometry...Traceback (most recent call last): File "manage.py", line 21, in <module> main() File "manage.py", line 17, in main execute_from_command_line(sys.argv) File "C:\Users\Marco\Envs\um\lib\site-packages\django\core\management\__init__.py", line 401, in execute_from_command_line utility.execute() File "C:\Users\Marco\Envs\um\lib\site-packages\django\core\management\__init__.py", line 395, in execute self.fetch_command(subcommand).run_from_argv(self.argv) File "C:\Users\Marco\Envs\um\lib\site-packages\django\core\management\base.py", line 328, in run_from_argv self.execute(*args, **cmd_options) File "C:\Users\Marco\Envs\um\lib\site-packages\django\core\management\base.py", line 369, in execute output = self.handle(*args, **options) File "C:\Users\Marco\Envs\um\lib\site-packages\django\core\management\base.py", line 83, in wrapped res = handle_func(*args, **kwargs) File "C:\Users\Marco\Envs\um\lib\site-packages\django\core\management\commands\migrate.py", line 231, in handle post_migrate_state = executor.migrate( File "C:\Users\Marco\Envs\um\lib\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 "C:\Users\Marco\Envs\um\lib\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 "C:\Users\Marco\Envs\um\lib\site-packages\django\db\migrations\executor.py", line 245, in apply_migration state = migration.apply(state, schema_editor) File "C:\Users\Marco\Envs\um\lib\site-packages\django\db\migrations\migration.py", line 124, in apply operation.database_forwards(self.app_label, schema_editor, old_state, project_state) File "C:\Users\Marco\Envs\um\lib\site-packages\django\db\migrations\operations\fields.py", line 110, in database_forwards schema_editor.add_field( File "C:\Users\Marco\Envs\um\lib\site-packages\django\db\backends\base\schema.py", line 450, in add_field definition, params = self.column_sql(model, field, include_default=True) File "C:\Users\Marco\Envs\um\lib\site-packages\django\db\backends\base\schema.py", line 223, in column_sql default_value = self.effective_default(field) File "C:\Users\Marco\Envs\um\lib\site-packages\django\db\backends\base\schema.py", line 303, in effective_default return field.get_db_prep_save(self._effective_default(field), self.connection) File "C:\Users\Marco\Envs\um\lib\site-packages\django\db\models\fields\__init__.py", line 821, in get_db_prep_save return self.get_db_prep_value(value, connection=connection, prepared=False) File "C:\Users\Marco\Envs\um\lib\site-packages\django\contrib\gis\db\models\fields.py", line 147, in get_db_prep_value super().get_db_prep_value(value, connection, *args, **kwargs), File "C:\Users\Marco\Envs\um\lib\site-packages\django\db\models\fields\__init__.py", line 816, in get_db_prep_value value = self.get_prep_value(value) File "C:\Users\Marco\Envs\um\lib\site-packages\django\contrib\gis\db\models\fields.py", line 190, in get_prep_value raise ValueError('Cannot use object with type %s for a spatial lookup parameter.' % type(obj).__name__) ValueError: Cannot use object with type int for a spatial lookup parameter.

I also tried to remove attributes from my model but nothing changes. The following is my models.py

from django.contrib.gis.db import models # Create your models here. class Piano(models.Model): """Modello che rappresenta un piano""" titolo = models.CharField(max_length=100, help_text='Nome del piano') acronimo = models.CharField(max_length=100, help_text='Acronimo del piano') #fk_territorio = models.ForeignKey('Territorio', verbose_name='Territorio', on_delete=models.SET_NULL, null=True) def __str__(self): """String for representing the Model object.""" return self.titolo class Meta: verbose_name_plural = "Piani" class Territorio(models.Model): """Modello che rappresenta la tipologia di una norma""" nome = models.CharField(max_length=100, help_text='Nome del territorio') fk_tipo_territorio = models.ForeignKey('TipoTerritorio', verbose_name='Tipo Territorio', on_delete=models.SET_NULL, null=True) parent = models.ForeignKey('self', blank=True, related_name='child', help_text='Parent del Territorio', on_delete=models.SET_NULL, null=True) codice = models.PositiveIntegerField(help_text='Codice del Territorio', null=True) geometry = models.GeometryField(spatial_index=True, null=True) def __str__(self): """String for representing the Model object.""" return self.nome class Meta: verbose_name_plural = "Territori" class TipoTerritorio(models.Model): """Modello che rappresenta la tipologia di una norma""" nome = models.CharField(max_length=100, help_text='Tipologia di territorio') def __str__(self): """String for representing the Model object.""" return self.nome class Meta: verbose_name_plural = "TipiTerritorio"

I am relatively new to Django and GeoDjango and I might be overlooking something. Any Idea on how to solve the migrate error?

EDIT: added 0008_territorio_geometry.py

# Generated by Django 3.0.4 on 2020-04-06 13:19 import django.contrib.gis.db.models.fields from django.db import migrations class Migration(migrations.Migration): dependencies = [ ('map', '0007_auto_20200406_1506'), ] operations = [ migrations.AddField( model_name='territorio', name='geometry', field=django.contrib.gis.db.models.fields.GeometryField(default=0, srid=4326), preserve_default=False, ), ]
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    Can you show the migration file 0008? (btw, don't call your FK fields fk_..., they are not ids when you access them, they are actual instances of the model they refer to: territorio.fk_tipo_territorio will return an instance of TipoTerritorio so just call it territorio.tipo_territorio). Commented Apr 7, 2020 at 9:48
  • Thanks for the suggestion about the FK fields, I added the migration file in the question Commented Apr 7, 2020 at 10:22

2 Answers 2

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You are adding the geometry field after the initial Territorio model creation, but you are not providing a default value to the field.
In order to apply this migration, Django asked you (in the terminal after the ./manage.py makemigrations part) to provide a default value manually for any existing records in the table. You must have answered 0 to that question and thus the problem arises (you have essentially added an Integer value to a Geometry field).

Since you are allowing null=True to the geometry field, the easy fix would be to:

  1. Revert the migrations to the previous one (0007_auto_20200406_1506):

    ./manage.py migrate my_app 0007_auto_20200406_1506

  2. Delete the migration file 0008_territorio_geometry.py.

  3. Check the table django_migrations in your DB for the entry 0008_territorio_geometry and remove that as well (if it exists).

  4. Provide a default value of None to the geometry field as follows:

    geometry = models.GeometryField(spatial_index=True, null=True, default=None)

  5. Recreate the migration naming it as you like, and then apply it:

    ./manage.py makemigrations --name 0008_territorio_geometry ./manage.py migrate

You should be set to go :)

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3 Comments

step 3 is unnecessary since ./manage.py migrate my_app 0007 will remove it from db
@suhailvs Indeed, but it is always good to double-check (that is why I added the "if exists" part) I have met some cases (with multiple DBs in the same project) where the migration was not removed.
What you described is exactly what happended: I have entered 0 as a default value from the command line, I thought I was entering the value for the IntegerField. Thanks a lot!
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`

dependencies = [ ('map', '0007_auto_20200406_1506'), ] operations = [ migrations.AddField( model_name='territorio', name='geometry', field=django.contrib.gis.db.models.fields.GeometryField(default=0, srid=4326), preserve_default=False, ), ]`

changes

`

dependencies = [ ('map', '0007_auto_20200406_1506'), ] operations = [ migrations.AddField( model_name='territorio', name='geometry', field=django.contrib.gis.db.models.fields.GeometryField(default=0, srid=4326), preserve_default=None, ), ]`
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Could you please provide some explanations or comments in addition to code?

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