在下面的最小示例中，我们有一个包含自引用外键的表。我想使用 sqlite 作为我的数据库并激活 PRAGMA foreign_keys。为了不关心向事务添加行的顺序，我想设置 PRAGMA defer_foreign_keys = ON。
我发现的奇怪的事情是，如果我使用内存中的 sqlite，这可以很好地工作，但是如果我使用数据库文件，它会抛出“FOREIGN KEY 约束失败”。这是怎么回事？
from pathlib import Path
from typing import Any, TYPE_CHECKING
import sqlalchemy.orm
from sqlalchemy import Column, ForeignKey, Integer, String, create_engine, event
from sqlalchemy.ext.declarative import declarative_base
if TYPE_CHECKING:
from sqlalchemy.pool import _ConnectionRecord # noqa
Base = declarative_base()
class User(Base):
__tablename__ = "users"
id = Column(Integer, primary_key=True)
name = Column(String)
parent_user_id = Column(ForeignKey("users.id"))
def main():
# Using a database file, results in FOREIGN KEY constraint failed
if Path("test_database.db").exists():
Path("test_database.db").unlink()
engine = create_engine("sqlite:///test_database.db")
# Using in-memory works as expected
# engine = create_engine("sqlite:///:memory:")
@event.listens_for(engine, "connect")
def set_sqlite_pragma(
dbapi_connection: Any, connection_record: "_ConnectionRecord"
) -> None:
if engine.name == "sqlite":
cursor = dbapi_connection.cursor()
cursor.execute("PRAGMA foreign_keys=ON")
cursor.close()
Base.metadata.drop_all(engine)
Base.metadata.create_all(engine)
session = sqlalchemy.orm.Session(autocommit=False, autoflush=False, bind=engine)
user_1 = User(id=1, name="Bob", parent_user_id=2)
user_2 = User(id=2, name="John Doe")
session.add_all([user_1, user_2])
session.execute("PRAGMA defer_foreign_keys = ON")
session.commit()
if __name__ == "__main__":
main()
import sqlite3
sqlite3.sqlite_version
'3.22.0'
追溯：
Traceback (most recent call last):
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1256, in _execute_context
self.dialect.do_executemany(
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/engine/default.py", line 606, in do_executemany
cursor.executemany(statement, parameters)
sqlite3.IntegrityError: FOREIGN KEY constraint failed
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "/home/finswimmer/tmp/minimal-alchemy/minimal_alchemy/example.py", line 53, in <module>
main()
File "/home/finswimmer/tmp/minimal-alchemy/minimal_alchemy/example.py", line 49, in main
session.commit()
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 1046, in commit
self.transaction.commit()
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 504, in commit
self._prepare_impl()
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 483, in _prepare_impl
self.session.flush()
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 2540, in flush
self._flush(objects)
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 2682, in _flush
transaction.rollback(_capture_exception=True)
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/util/langhelpers.py", line 68, in __exit__
compat.raise_(
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/util/compat.py", line 182, in raise_
raise exception
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 2642, in _flush
flush_context.execute()
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/orm/unitofwork.py", line 422, in execute
rec.execute(self)
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/orm/unitofwork.py", line 586, in execute
persistence.save_obj(
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/orm/persistence.py", line 239, in save_obj
_emit_insert_statements(
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/orm/persistence.py", line 1083, in _emit_insert_statements
c = cached_connections[connection].execute(statement, multiparams)
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1011, in execute
return meth(self, multiparams, params)
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/sql/elements.py", line 298, in _execute_on_connection
return connection._execute_clauseelement(self, multiparams, params)
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1124, in _execute_clauseelement
ret = self._execute_context(
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1316, in _execute_context
self._handle_dbapi_exception(
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1510, in _handle_dbapi_exception
util.raise_(
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/util/compat.py", line 182, in raise_
raise exception
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1256, in _execute_context
self.dialect.do_executemany(
File "/home/finswimmer/tmp/minimal-alchemy/.venv/lib/python3.9/site-packages/sqlalchemy/engine/default.py", line 606, in do_executemany
cursor.executemany(statement, parameters)
sqlalchemy.exc.IntegrityError: (sqlite3.IntegrityError) FOREIGN KEY constraint failed
[SQL: INSERT INTO users (id, name, parent_user_id) VALUES (?, ?, ?)]
[parameters: ((1, 'Bob', 2), (2, 'John Doe', None))]
(Background on this error at: http://sqlalche.me/e/13/gkpj)
更新：
使用普通的 sqlite3 似乎没有问题：
import sqlite3
from pathlib import Path
table = """
CREATE TABLE users (
id INTEGER NOT NULL,
name VARCHAR,
parent_user_id INTEGER,
PRIMARY KEY (id),
FOREIGN KEY(parent_user_id) REFERENCES users (id)
)
"""
def main():
if Path("example.db").exists():
Path("example.db").unlink()
connection = sqlite3.connect("example.db")
cursor = connection.cursor()
cursor.execute(table)
cursor.execute("PRAGMA foreign_keys=ON")
cursor.execute("PRAGMA defer_foreign_keys=ON")
users = [(1, "Bob", 2), (2, "John Doe", None)]
cursor.executemany("INSERT INTO users VALUES (?,?,?)", users)
connection.commit()
if __name__ == "__main__":
main()
答案 0 :(得分：0)
解决方法：使用上下文管理器暂时禁用外键检查，然后运行 ","c。
Public Class Form1
Private ReadOnly Polish As New System.Globalization.CultureInfo("pl-PL")
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim Numbers_in_String_Array As String() = {"22.000", "0.00", "-22.00"}
Dim Numbers_in_String_Array_new(Numbers_in_String_Array.Length - 1) As String
For i As Integer = 0 To Numbers_in_String_Array.Length - 1 Step 1
Numbers_in_String_Array_new(i) = Numbers_in_String_Array(i).Replace("."c, ","c)
Next
Dim value As Double
Dim successful As Boolean
Dim Numbers_in_String_Array_new_new(Numbers_in_String_Array.Length - 1) As String
For i As Integer = 0 To Numbers_in_String_Array_new.Length - 1 Step 1
successful = Double.TryParse(Numbers_in_String_Array_new(i), value)
If successful Then
Debug.WriteLine("did work")
Else
Debug.WriteLine("did not work")
End If
If value < 0.0 Then
Debug.WriteLine("negative number")
Numbers_in_String_Array_new_new(i) = (value * (-1.0)).ToString(Polish)
ElseIf value = 0.0 Then
Debug.WriteLine("0")
Numbers_in_String_Array_new_new(i) = (value * (-1.0)).ToString(Polish)
ElseIf value > 0.0 Then
Debug.WriteLine("positive number")
Numbers_in_String_Array_new_new(i) = (value * (-1.0)).ToString(Polish)
End If
Next
End Sub
End Class