【发布时间】：2017-09-27 15:36:26
【问题描述】：
我正在尝试将我的一个 django 项目的数据库从 sqlite 迁移到 mysql。我首先用./manage.py dumpdata > dump.json 转储了整个数据，然后用./manage.py migrate 准备了数据库，并删除了表中所有创建的数据（这是必要的，因为转储包含所有数据）。
当我想用./manage.py loaddata将数据导入新数据库时，我能够解决很多错误，但我找不到这个错误的根源：
Processed 330984 object(s).Traceback (most recent call last):
File "/app/manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/usr/local/lib/python3.5/site-packages/django/core/management/__init__.py", line 363, in execute_from_command_line
utility.execute()
File "/usr/local/lib/python3.5/site-packages/django/core/management/__init__.py", line 355, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/lib/python3.5/site-packages/django/core/management/base.py", line 283, in run_from_argv
self.execute(*args, **cmd_options)
File "/usr/local/lib/python3.5/site-packages/django/core/management/base.py", line 330, in execute
output = self.handle(*args, **options)
File "/usr/local/lib/python3.5/site-packages/django/core/management/commands/loaddata.py", line 69, in handle
self.loaddata(fixture_labels)
File "/usr/local/lib/python3.5/site-packages/django/core/management/commands/loaddata.py", line 109, in loaddata
self.load_label(fixture_label)
File "/usr/local/lib/python3.5/site-packages/django/core/management/commands/loaddata.py", line 175, in load_label
obj.save(using=self.using)
File "/usr/local/lib/python3.5/site-packages/django/core/serializers/base.py", line 205, in save
models.Model.save_base(self.object, using=using, raw=True, **kwargs)
File "/usr/local/lib/python3.5/site-packages/django/db/models/base.py", line 837, in save_base
updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
File "/usr/local/lib/python3.5/site-packages/django/db/models/base.py", line 904, in _save_table
forced_update)
File "/usr/local/lib/python3.5/site-packages/django/db/models/base.py", line 954, in _do_update
return filtered._update(values) > 0
File "/usr/local/lib/python3.5/site-packages/django/db/models/query.py", line 664, in _update
return query.get_compiler(self.db).execute_sql(CURSOR)
File "/usr/local/lib/python3.5/site-packages/django/db/models/sql/compiler.py", line 1199, in execute_sql
cursor = super(SQLUpdateCompiler, self).execute_sql(result_type)
File "/usr/local/lib/python3.5/site-packages/django/db/models/sql/compiler.py", line 894, in execute_sql
raise original_exception
File "/usr/local/lib/python3.5/site-packages/django/db/models/sql/compiler.py", line 884, in execute_sql
cursor.execute(sql, params)
File "/usr/local/lib/python3.5/site-packages/django/db/backends/utils.py", line 60, in execute
self.db.validate_no_broken_transaction()
File "/usr/local/lib/python3.5/site-packages/django/db/backends/base/base.py", line 448, in validate_no_broken_transaction
"An error occurred in the current transaction. You can't "
django.db.transaction.TransactionManagementError: Problem installing fixture '/path/to/django/dump.json': Could not load auth.User(pk=1): An error occurred in the current transaction. You can't execute queries until the end of the 'atomic' block.
我已经尝试删除所有的信号接收器，这样在执行 loaddata 时我自己的代码都不会运行。
有没有其他人在使用 django 的 loaddata 时遇到过类似的行为并设法让它工作？
上下文：
- python v3.5
- django v1.11.4
- 仅使用 stdlib django 模型字段
【问题讨论】：
-
如果你可以使用 Postgresql 代替 Mysql，我认为它可以更优雅地处理并发。
-
是的，事实上，我可以。我认为这个错误似乎与 django 相关，或者您认为使用 Postgresql 会使其消失？
-
PG 使用 MVCC（多版本并发控制）。我猜现代 Mysql 实例可能会使用 MVCC，但我不知道这是否是默认设置。
-
MySQL 5.7（我正在使用）似乎使用 MVCC（dev.mysql.com/doc/refman/5.7/en/innodb-multi-versioning.html）。这使得对 Postgresql 的更改不太可能解决这个问题 - 如果这是问题的话。
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这个 Pg/MySQL 辩论是一个已知的火焰战源。我在 Postgresql 方面，我认为你应该试一试。也就是说，这只是一种意见，为什么这是评论而不是答案。
标签： django