我试图在PostgreSQL 9.6.5数据库上运行Django 1.11迁移,但得到一个奇怪的错误:
Applying myapp.0011_auto_20171130_1807...Traceback (most recent call last):
File "manage.py", line 9, in <module>
execute_from_command_line(sys.argv)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 364, in execute_from_command_line
utility.execute()
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 356, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/core/management/base.py", line 283, in run_from_argv
self.execute(*args, **cmd_options)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/core/management/base.py", line 330, in execute
output = self.handle(*args, **options)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/core/management/commands/migrate.py", line 204, in handle
fake_initial=fake_initial,
File "/usr/local/myproject/.env/local/lib/python2.7/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 "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 145, in _migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 244, in apply_migration
state = migration.apply(state, schema_editor)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/migrations/migration.py", line 129, in apply
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/migrations/operations/models.py", line 536, in database_forwards
getattr(new_model._meta, self.option_name, set()),
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/backends/base/schema.py", line 349, in alter_unique_together
self._delete_composed_index(model, fields, {'unique': True}, self.sql_delete_unique)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/backends/base/schema.py", line 380, in _delete_composed_index
self.execute(self._delete_constraint_sql(sql, model, constraint_names[0]))
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/backends/base/schema.py", line 120, in execute
cursor.execute(sql, params)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/utils.py", line 94, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/usr/local/myproject/.env/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: constraint "idx_32269_myapp_mymodel_title_333195ae82ac2107_uniq" of relation "myapp_mymodel" does not exist
迁移正在将一个唯一的契约从包含一列改为包含两列。很简单。在创建新索引之前,它需要销毁旧索引“idx_32269_myapp_mymodel_title_333195ae82ac2107_uniq”。然而,它失败了,因为它不认为旧的存在。在
因此,我用pgadminiiii连接到数据库并检查了表,与错误消息相反,该表确实有一个名为idx_32269_myapp_mymodel_title_333195ae82ac2107_uniq
的索引。在
我想Django可能使用了稍微不同的连接参数,并且连接到了一个不同的数据库?让我们试着从Django dbshell中检查它。所以我开始manage.py dbshell
并运行:
它返回了一行。在
为什么Django在迁移过程中无法看到这个索引,即使该索引肯定存在于数据库中?在
问题是,我使用工具pgloader将数据库从MySQL转换为PostgreSQL,这个工具通过在PostgreSQL中创建索引来转换约束,而Django PG后端将其作为约束创建。因此,当迁移运行时,它只查找约束,而找不到任何约束。
我通过删除索引并将其重新创建为真正的约束来修复此问题:
之后,Django迁移正常运行。
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