Migration to remove a GIS field causes exception

[James Aylett]

A GIS model which contains a PointField:

from django.contrib.gis.db import models

class Event(models.Model):
    ...
    location = models.PointField(geography=True, blank=True, null=True)

migrated to successfully, then removed with an autogenerated migration:

class Migration(migrations.Migration):

    operations = [
        migrations.RemoveField(
            model_name='event',
            name='location',
        ),
    ]

when applied (1.7rc2, postgresql 9.3, postgis 1.5.3) raises the following exception:

 File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/home/user/.virtualenvs/looseend/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
    utility.execute()
  File "/home/user/.virtualenvs/looseend/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 377, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/user/.virtualenvs/looseend/local/lib/python2.7/site-packages/django/core/management/base.py", line 288, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/home/user/.virtualenvs/looseend/local/lib/python2.7/site-packages/django/core/management/base.py", line 337, in execute
    output = self.handle(*args, **options)
  File "/home/user/.virtualenvs/looseend/local/lib/python2.7/site-packages/django/core/management/commands/migrate.py", line 160, in handle
    executor.migrate(targets, plan, fake=options.get("fake", False))
  File "/home/user/.virtualenvs/looseend/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 63, in migrate
    self.apply_migration(migration, fake=fake)
  File "/home/user/.virtualenvs/looseend/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 97, in apply_migration
    migration.apply(project_state, schema_editor)
  File "/home/user/.virtualenvs/looseend/local/lib/python2.7/site-packages/django/db/migrations/migration.py", line 107, in apply
    operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
  File "/home/user/.virtualenvs/looseend/local/lib/python2.7/site-packages/django/db/migrations/operations/fields.py", line 84, in database_forwards
    schema_editor.remove_field(from_model, from_model._meta.get_field_by_name(self.name)[0])
  File "/home/user/.virtualenvs/looseend/local/lib/python2.7/site-packages/django/contrib/gis/db/backends/postgis/schema.py", line 108, in remove_field
    "column": self.geo_quote_name(field.column),
  File "/home/user/.virtualenvs/looseend/local/lib/python2.7/site-packages/django/db/backends/schema.py", line 98, in execute
    cursor.execute(sql, params)
  File "/home/user/.virtualenvs/looseend/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 81, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/home/user/.virtualenvs/looseend/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
  File "/home/user/.virtualenvs/looseend/local/lib/python2.7/site-packages/django/db/utils.py", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/home/user/.virtualenvs/looseend/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
django.db.utils.InternalError: column not found in geometry_columns table
CONTEXT:  SQL statement "SELECT DropGeometryColumn('','',$1,$2)"
PL/pgSQL function "dropgeometrycolumn" line 5 at SQL statement

There is indeed nothing in geometry_columns, however running SELECT Probe_Geometry_Columns(); doesn't indicate a desire from postgis for there to be any either.

The migration fragment that created the column (which was under 1.7b4 I believe) is (as part of a migrations.CreateModel() call):

('location', django.contrib.gis.db.models.fields.PointField(srid=4326, geography=True)),

The entire app has been built under 1.7, and all project app DDL has gone through the migrations framework.

[Andrew Godwin]

Initial investigation leads me to believe this is only happening when geography=true.

[Andrew Godwin <andrew@…>]

In d4f62a7ae7bed98f3ee3f5c9a76f5591ec7841fd:

Fixed #23161: Drop PostGIS geography fields correctly

[Andrew Godwin <andrew@…>]

In d77f92fa1ee473160f50ab8482876e4bab33f8cf:

[1.7.x] Fixed #23161: Drop PostGIS geography fields correctly