How to set cascade option in sqlmodel, I want to delete all the childrens when parent is deleted #213
Comments
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Please find the updated example code below |
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I have managed to achieve this by using the legacy SQLAlchemy relationship features by passing the sa_relationship parameter. |
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You can pass the cascade delete parameters through class User(UserBase, table=True):
addresses: List["UserAddress"] = Relationship(sa_relationship_kwargs={"cascade": "delete"}, back_populates="user_address")Granted, I wasn't able to get it to work with from typing import List, Optional
from sqlmodel import Field, Relationship, Session, SQLModel, create_engine
class Hero(SQLModel, table=True):
id: Optional[int] = Field(default=None, primary_key=True)
tests: List["Test"] = Relationship(
sa_relationship_kwargs={"cascade": "delete"}
# Doesn't work vvv
# sa_relationship_kwargs={"cascade": "all, delete"}
)
class Test(SQLModel, table=True):
id: Optional[int] = Field(default=None, primary_key=True)
hero_id: Optional[int] = Field(default=None, foreign_key="hero.id")
engine = create_engine("sqlite:///", echo=True)
def create_db_and_tables():
SQLModel.metadata.create_all(engine)
def create_heroes():
hero = Hero(name="Deadpond", secret_name="Dive Wilson")
t1 = Test()
t2 = Test()
hero.tests = [t1, t2]
with Session(engine) as session:
session.add(hero)
session.commit()
session.query(Hero).delete()
session.commit()
heroes = session.query(Hero).all()
print(heroes)
assert len(heroes) == 0
tests = session.query(Test).all()
print(tests)
assert len(tests) == 0
def main(): #
create_db_and_tables() #
create_heroes() #
if __name__ == "__main__": #
main()
"""
2022-01-13 15:37:54,273 INFO sqlalchemy.engine.Engine DELETE FROM hero
2022-01-13 15:37:54,273 INFO sqlalchemy.engine.Engine [generated in 0.00006s] ()
2022-01-13 15:37:54,273 INFO sqlalchemy.engine.Engine COMMIT
2022-01-13 15:37:54,273 INFO sqlalchemy.engine.Engine BEGIN (implicit)
2022-01-13 15:37:54,274 INFO sqlalchemy.engine.Engine SELECT hero.id AS hero_id
FROM hero
2022-01-13 15:37:54,274 INFO sqlalchemy.engine.Engine [generated in 0.00006s] ()
[]
2022-01-13 15:37:54,275 INFO sqlalchemy.engine.Engine SELECT test.id AS test_id, test.hero_id AS test_hero_id
FROM test
2022-01-13 15:37:54,275 INFO sqlalchemy.engine.Engine [generated in 0.00006s] ()
[]
2022-01-13 15:37:54,275 INFO sqlalchemy.engine.Engine ROLLBACK
""" |
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Following up on my response above. For SQLite engines foreign key constraints are disabled by default. SQLAlchemy provides the ability to enable this per connection via an event listener documented here: https://docs.sqlalchemy.org/en/13/dialects/sqlite.html#foreign-key-support I believe what I posted above is likely not the correct way to implement this. Instead, I believe you should set the constraint on the column instead of the relationship which will use the DB to resolve the constraint as opposed to the ORM. You should then set the Therefore the updated code should read something like the following: # SQLite specific
from sqlalchemy.engine import Engine
from sqlalchemy import event
from sqlite3 import Connection as SQLite3Connection
@event.listens_for(Engine, "connect")
def set_sqlite_pragma(dbapi_connection, connection_record):
if isinstance(dbapi_connection, SQLite3Connection):
cursor = dbapi_connection.cursor()
cursor.execute("PRAGMA foreign_keys=ON")
cursor.close()
# Update models
class Hero(SQLModel, table=True):
id: Optional[int] = Field(default=None, primary_key=True)
tests: List["Test"] = Relationship(
sa_relationship_kwargs={
"cascade": "all, delete", # Instruct the ORM how to track changes to local objects
},
)
class Test(SQLModel, table=True):
id: Optional[int] = Field(default=None, primary_key=True)
hero_id: Optional[int] = Field(
sa_column=Column(Integer, ForeignKey("hero.id", ondelete="CASCADE")) # Set the foreign key behavior on the table metadata
) |
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@JLHasson why does your relationship not have a back_populates kwarg? |
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As far as I know it's an optional parameter, you just need it if you want the value to be filled on the object the relation is to. You should be able to add it here I believe without issue? |
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Hello, guys, I have a When I delete the from typing import Optional
from sqlmodel import Field, SQLModel,create_engine, Session
class Worker(SQLModel, table=True):
id: Optional[int] = Field(default=None, primary_key=True)
name: str = Field(index=True)
class Transaction(SQLModel, table=True):
id: Optional[int] = Field(default=None, primary_key=True)
worker_id: int = Field(index=True, foreign_key="worker.id")
sqlite_file_name = "database/database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"
engine = create_engine(sqlite_url, echo=False)
SQLModel.metadata.create_all(engine)
# Create a worker
with Session(engine) as session:
worker = Worker(name='Worker 1')
session.add(worker)
session.commit()
session.refresh(worker)
# Create a transaction pointing to this worker
with Session(engine) as session:
transaction = Transaction(worker_id=worker.id)
session.add(transaction)
session.commit()
session.refresh(transaction)
# Delete the worker
with Session(engine) as session:
session.delete(worker)
session.commit()
# Print all transactions on database
with Session(engine) as session:
transactions = session.query(Transaction).all()
print(transactions)What I was expecting: Does anyone know why this transaction is still pointing to |
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I have achieved the behaviour I was looking for by creating a class Worker(SQLModel, table=True):
id: Optional[int] = Field(default=None, primary_key=True)
name: str = Field(index=True)
transactions: List["Transaction"] = Relationship(
sa_relationship_kwargs={
"cascade": ""
}
)Also, class Transaction(SQLModel, table=True):
id: Optional[int] = Field(default=None, primary_key=True)
worker_id: Optional[int] = Field(index=True, foreign_key="worker.id")The whole code becomes: from typing import Optional, List
from sqlmodel import Field, SQLModel, create_engine, Session, Relationship
class Worker(SQLModel, table=True):
id: Optional[int] = Field(default=None, primary_key=True)
name: str = Field(index=True)
transactions: List["Transaction"] = Relationship(
sa_relationship_kwargs={
"cascade": ""
}
)
class Transaction(SQLModel, table=True):
id: Optional[int] = Field(default=None, primary_key=True)
worker_id: Optional[int] = Field(index=True, foreign_key="worker.id")
sqlite_file_name = "database/database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"
engine = create_engine(sqlite_url, echo=False)
SQLModel.metadata.create_all(engine)
# Create a worker
with Session(engine) as session:
worker = Worker(name='Worker 1')
session.add(worker)
session.commit()
session.refresh(worker)
# Create a transaction pointing to this worker
with Session(engine) as session:
transaction = Transaction(worker_id=worker.id)
session.add(transaction)
session.commit()
session.refresh(transaction)
# Delete the worker
with Session(engine) as session:
session.delete(worker)
session.commit()
# Print all transactions on database
with Session(engine) as session:
transactions = session.query(Transaction).all()
print(transactions)The output: >>> [Transaction(worker_id=None, id=1)] |
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worked by setting |
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For anyone else struggling with this, recommend pinning |
basiltt
changed the title
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Why not implement something like this and avoid use SQLAlchemy? class MyModel(SQLModel, table=True):
id: str
fk_id: str = Field(
foreign_key=f"{SchemaName.non_performing_loans.value}.{tenant_name}.tenant_id",
default=None,
description="Tenant id",
delete="cascade"
) |
@GiorgioSgl It doesn't seem like sqlmodel |
First Check
Commit to Help
Example Code
Description
I couldn't find any samples to delete the children's of a parent when it is deleted.
Operating System
Windows
Operating System Details
Windows 10 20H2
SQLModel Version
sqlmodel==0.0.6
Python Version
Python 3.9.9
Additional Context
No response
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