问题描述
我正在设计我们的数据库,并在 Session
架构中有一个名为 common_exp
的表,其定义如下:
@schema
class Session(dj.Manual):
deFinition = """ # information about the session and experimental setup
-> common_mice.Mouse
day : date # Date of the experimental session (YYYY-MM-DD)
trial : tinyint # Counter of experimental sessions on the same day (base 1)
---
id : varchar(128) # Unique identifier
path : varchar(256) # Relative path of this session on the server
counter : smallint # Overall counter of all sessions across mice (base 0)
experimenter : varchar(128) # Who actually performed the experiment,must be a username from Investigator
-> Anesthesia
-> Setup
-> Task
notes : varchar(2048) # description of important things that happened
"""
我想更改某些属性的名称,因此想删除该表。但是,我遇到了这个错误:
common_exp.Session().drop()
`common_exp`.`session` (0 tuples)
Proceed? [yes,No]: >? yes
Traceback (most recent call last):
File "C:\Anaconda3\envs\datajoint_wahl\lib\site-packages\IPython\core\interactiveshell.py",line 3441,in run_code
exec(code_obj,self.user_global_ns,self.user_ns)
File "<ipython-input-4-bce682713228>",line 1,in <module>
common_exp.Session().drop()
File "C:\Anaconda3\envs\datajoint_wahl\lib\site-packages\datajoint\table.py",line 474,in drop
FreeTable(self.connection,table).drop_quick()
File "C:\Anaconda3\envs\datajoint_wahl\lib\site-packages\datajoint\table.py",line 450,in drop_quick
self.connection.query(query)
File "C:\Anaconda3\envs\datajoint_wahl\lib\site-packages\datajoint\connection.py",line 302,in query
self._execute_query(cursor,query,args,suppress_warnings)
File "C:\Anaconda3\envs\datajoint_wahl\lib\site-packages\datajoint\connection.py",line 268,in _execute_query
raise translate_query_error(err,query)
File "C:\Anaconda3\envs\datajoint_wahl\lib\site-packages\datajoint\connection.py",line 266,in _execute_query
cursor.execute(query,args)
File "C:\Anaconda3\envs\datajoint_wahl\lib\site-packages\pyMysqL\cursors.py",line 148,in execute
result = self._query(query)
File "C:\Anaconda3\envs\datajoint_wahl\lib\site-packages\pyMysqL\cursors.py",line 310,in _query
conn.query(q)
File "C:\Anaconda3\envs\datajoint_wahl\lib\site-packages\pyMysqL\connections.py",line 548,in query
self._affected_rows = self._read_query_result(unbuffered=unbuffered)
File "C:\Anaconda3\envs\datajoint_wahl\lib\site-packages\pyMysqL\connections.py",line 775,in _read_query_result
result.read()
File "C:\Anaconda3\envs\datajoint_wahl\lib\site-packages\pyMysqL\connections.py",line 1156,in read
first_packet = self.connection._read_packet()
File "C:\Anaconda3\envs\datajoint_wahl\lib\site-packages\pyMysqL\connections.py",line 725,in _read_packet
packet.raise_for_error()
File "C:\Anaconda3\envs\datajoint_wahl\lib\site-packages\pyMysqL\protocol.py",line 221,in raise_for_error
err.raise_MysqL_exception(self._data)
File "C:\Anaconda3\envs\datajoint_wahl\lib\site-packages\pyMysqL\err.py",line 143,in raise_MysqL_exception
raise errorclass(errno,errval)
pyMysqL.err.IntegrityError: (1217,'Cannot delete or update a parent row: a foreign key constraint fails')
如您所见,该表是空的,并且没有进一步的依赖项。错误消息也没有告诉我是哪个键造成了问题,或者哪个其他表,所以我有点困惑问题可能出在哪里。
我使用 root 帐户访问数据库,所以权限应该不是问题。从其他模式中删除表是有效的,只是这个模式会产生这个错误。
解决方法
此错误表示在可以删除 common_exp.Session
之前需要删除 Session
下游的依赖表。
通常,DataJoint 将级联并删除所有下游表。但是,有时 DataJoint 看不到依赖表,因为它们位于尚未加载的不同架构中。您将需要加载进行此引用的架构,以允许 DataJoint 级联放置。您可以使用 dj.list_schemas()
查看所有可用的架构。
感谢您的提问-
基于表中没有记录但删除失败并出现此错误这一事实,似乎确实存在使用外键定义的下游表返回会话表,因此删除会话表会留下这些表“孤立”,从而造成完整性错误。从示例中并不清楚情况并非如此。
以下 SQL 查询在架构级别检查正向/反向依赖关系(回答问题:“哪个架构取决于哪些其他架构”):
SELECT distinct(UNIQUE_CONSTRAINT_SCHEMA)
FROM information_schema.REFERENTIAL_CONSTRAINTS
where constraint_schema='my_schema'; -- forward dependencies for 'my_schema'
SELECT distinct(CONSTRAINT_SCHEMA)
FROM information_schema.REFERENTIAL_CONSTRAINTS
where unique_constraint_schema='my_schema'; -- reverse dependencies for 'my_schema'
不幸的是,我不记得确切的列,但信息架构中也提供了表级信息。