为PostgreSQL部署定义唯一约束

Question

我正在尝试部署到Heroku并从sqlite3转换为postgres。

给定的Showtime是指电影和场地。

我想我只是缺少某种模型设置声明，它将外键字段指定为唯一。

当我运行make migrations时，我收到以下错误。 Ť

  Applying venues.0018_auto_20170824_1907...Traceback (most recent call last):
  File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
psycopg2.ProgrammingError: there is no unique constraint matching given keys for referenced table "venues_venue"


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

Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "/app/.heroku/python/lib/python3.6/site-packages/django/core/management/__init__.py", line 363, in execute_from_c
ommand_line
    utility.execute()
  File "/app/.heroku/python/lib/python3.6/site-packages/django/core/management/__init__.py", line 355, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/app/.heroku/python/lib/python3.6/site-packages/django/core/management/base.py", line 283, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/app/.heroku/python/lib/python3.6/site-packages/django/core/management/base.py", line 330, in execute
    output = self.handle(*args, **options)
  File "/app/.heroku/python/lib/python3.6/site-packages/django/core/management/commands/migrate.py", line 204, in handle
    fake_initial=fake_initial,
  File "/app/.heroku/python/lib/python3.6/site-packages/django/db/migrations/executor.py", line 115, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/app/.heroku/python/lib/python3.6/site-packages/django/db/migrations/executor.py", line 145, in _migrate_all_for
wards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/app/.heroku/python/lib/python3.6/site-packages/django/db/migrations/executor.py", line 244, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/app/.heroku/python/lib/python3.6/site-packages/django/db/migrations/migration.py", line 129, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/app/.heroku/python/lib/python3.6/site-packages/django/db/migrations/operations/fields.py", line 216, in databas
e_forwards
    schema_editor.alter_field(from_model, from_field, to_field)
  File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 515, in alter_field
    old_db_params, new_db_params, strict)
  File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/postgresql/schema.py", line 112, in _alter_fi
eld
    new_db_params, strict,
  File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 773, in _alter_field
    self.execute(self._create_fk_sql(model, new_field, "_fk_%(to_table)s_%(to_column)s"))
  File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 120, in execute
    cursor.execute(sql, params)
  File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
  File "/app/.heroku/python/lib/python3.6/site-packages/django/db/utils.py", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/app/.heroku/python/lib/python3.6/site-packages/django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/app/.heroku/python/lib/python3.6/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: there is no unique constraint matching given keys for referenced table "venues_venue"



class Venue(models.Model):
name            = models.CharField(max_length=40, null=False, blank=False)
venue_id        = models.SmallIntegerField(unique=True, null=False, blank=False)

class Film(models.Model):
    title           = models.CharField(max_length=256, null=False, blank=False)
    film_id         = models.SmallIntegerField(unique=True, null=False, blank=False)

class Showtime(models.Model):
showtime_id     = models.SmallIntegerField(null=True, blank=True)
venue_id        = models.ForeignKey(Venue, to_field="venue_id", db_column="venue_id")
film_id         = models.ForeignKey(Film, to_field="film_id", db_column="film_id")