Could not refresh instance
AshikurRahman-sec opened this issue · comments
First Check
- I added a very descriptive title to this issue.
- I used the GitHub search to find a similar issue and didn't find it.
- I searched the SQLModel documentation, with the integrated search.
- I already searched in Google "How to X in SQLModel" and didn't find any information.
- I already read and followed all the tutorial in the docs and didn't find an answer.
- I already checked if it is not related to SQLModel but to Pydantic.
- I already checked if it is not related to SQLModel but to SQLAlchemy.
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- I commit to help with one of those options 👆
Example Code
from typing import Optional
from sqlmodel import Field, SQLModel
class Server(SQLModel, table=True):
id: Optional[int] = Field(default=None, primary_key=True)
ip: str
health_status: Optional[str] = None
cpu_cores: Optional[int] = None
@router.post("/add")
def add_server(item:Server):
return server_action.add_server(item)
def add_server(item):
with Session(engine) as session:
session.add(item)
session.commit()
session.refresh(item) # could not refresh instance
return item
Description
In sql model documentation I saw an example of session.refresh() but when I am trying to implement this in my fastapi project this not working and raise exception that is could not refresh instance and also I am trying to print item.id, this is not also working, raise exception that is expired.
Operating System
Linux
Operating System Details
No response
SQLModel Version
0.0.8
Python Version
3.10.6
Additional Context
raise sa_exc.InvalidRequestError(
sqlalchemy.exc.InvalidRequestError: Could not refresh instance '<Server at 0x7f69b549f500>'
database is mysql
del session.refresh(item)
add session.flush()
maybe work
@JeseYe thanks but I want to know why session.refresh not refresh item.
You cannot refresh the item because there is no database instance connected with it.
To do that you need to retrieve the item from the database using an select statement.
You can use refresh in the following:
- retrieve a instance from the database
hero = session.get(Hero, {'name': 'Hans'})
or a select statement - change attributes
hero.age=42
- add to session
session.add(hero)
- write changes
session.commit()
- refresh the instance collected from 1.
session.refresh(hero)
I'm running into this problem myself as well. Pardon my ignorance, but shouldn't SQLModel do this for us? Or is this just something that must be done when using MySQL (assuming this isn't a problem for other DB types)?
I discovered a solution for this:
As it turns out, the object I was passing to the REST endpoint had an ID specified (the ID was 0). When I either don't specify an ID or set it to None prior to adding/committing/refreshing then everything works as desired.
def add_server(item):
with Session(engine) as session:
if item.id == 0:
item.id = None
session.add(item)
session.commit()
session.refresh(item) # now refreshes properly!
return item
Although... again... shouldn't SQLModel (or FastAPI?) determine that since default=None
is specified that it pass id=None
inside the /docs
endpoint? Right now, it passes id=0
for the primary key when I assumed it would've passed id=None
...
id: Optional[int] = Field(default=None, primary_key=True)
Depends on what the default value in the Item schema is, whether 0 or None. However, we shouldn't be having to do this. Using an if condition to check for an id that is passed from a request seems like hacky fix to this problem. If the id is set as the primary key in the models it should be auto incremented by the orm.
I also have this (or, rather, a similar) issue. But in my case I do have both defaults that are not none, and a record with the same primary key in DB.
Code that doesn't work (right now at least)
Models
import uuid
import pydantic
from sqlmodel import Field, Relationship, SQLModel
from .faculty import FacultyModel
class CreateDepartment(SQLModel):
name: str = Field(unique=True, index=True)
description: str | None = Field(default=None, nullable=True)
class DepartmentRepresentation(BaseDepartment):
department_id: pydantic.UUID4
faculties: list[FacultyModel]
class DepartmentModel(BaseDepartment, table=True):
"""
Describes a department in an educational institution.
Highest level of organization in an educational institution.
Departments have a list of associated faculties.
"""
department_id: pydantic.UUID4 = Field(
default_factory=uuid.uuid4,
primary_key=True,
index=True,
)
faculties: list[FacultyModel] = Relationship(back_populates="department")
Endpoint
Code sample:
@admin_router.put(
"/department/{department_id}",
description="Update a department",
)
async def update_department(
db: Annotated[database_session_type, Depends(database_session)],
department_id: str,
department: Annotated[CreateDepartment, Body()],
_: Annotated[DepartmentModel, Depends(department_exists)],
) -> DepartmentRepresentation:
department_obj = DepartmentModel.model_validate(department)
department_obj.department_id = department_id
return update_entity(
db=db,
entity=department_obj,
)
Basically - it takes in the model for a department, and spits out it's representation from the database by performing an update.
I'm using model validation to convert input to the DB model, and set the foreign key to the one specified in path.
department_exists
just verifies that specified department_id
is valid and is present in the DB
Update call
from sqlalchemy.exc import IntegrityError, InvalidRequestError
from sqlmodel import Session, SQLModel
from samurai_backend.errors import SamuraiIntegrityError
...
def update_entity(
db: Session,
entity: SQLModel,
) -> SQLModel:
try:
db.add(entity)
db.commit()
db.refresh(entity)
return entity
except (IntegrityError, InvalidRequestError) as e:
db.rollback()
raise SamuraiIntegrityError from e
Error
I get exception InvalidRequestError
that looks like this:
(psycopg2.errors.UniqueViolation) duplicate key value violates unique constraint "departmentmodel_pkey"\nDETAIL: Key (department_id)=(1523095d-3d9d-46a7-bed5-2e19d3314712) already exists.\n\n[SQL: INSERT INTO departmentmodel (name, description, department_id)...
There's a lengthy INSERT SQL query, which is performed in db.commit()
line. Which is expected, I guess, but not helpful in this case.
Code that does work (right now)
Update the update_entity
and call to it by adding primary_key parameter. In my case it's department_id
, and the method now looks like this:
from sqlalchemy.exc import IntegrityError, InvalidRequestError
from sqlmodel import Session, SQLModel, update
from samurai_backend.errors import SamuraiIntegrityError
...
def update_entity(
db: Session,
entity: SQLModel,
primary_key: str,
) -> SQLModel:
try:
entity_class = entity.__class__
update_query = (
update(entity_class)
.where(getattr(entity_class, primary_key) == getattr(entity, primary_key))
.values(**entity.model_dump(exclude={primary_key}))
)
db.exec(update_query)
db.commit()
return entity
except (IntegrityError, InvalidRequestError) as e:
db.rollback()
raise SamuraiIntegrityError from e
Right now I see this as my only solution, but if you have different ideas, please, let me (or, rather - us) know.
P.S. Just using refresh won't do, since then you will get an error that this object is not in registry yet.
Thanks!
Additional info
I'm using sqlmodel 0.0.16, the latest version at the moment of writing this comment.
had a similar issue, setting auto_increment=True on primary_key id solved it