Advice for unique=True, max_length=30, min_length=3, that are causing a few problems

[tomislavm021]

First Check

• I added a very descriptive title here.
• I used the GitHub search to find a similar question 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.

Commit to Help

• I commit to help with one of those options 👆

Example Code

class Role(str, Enum):
    admin = "admin"
    superuser = "superuser"
    customer = "customer"

class User(SQLModel, table=True):
    __tablename__ = "users"
   
    uid: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True)  
    email: str = Field(unique=True, max_length=30, min_length=3)
    username: str = Field(unique=True, max_length=30, min_length=3)
    date_joined: datetime = Field(default_factory=datetime.now)
    updated_at: datetime = Field(default_factory=datetime.now)
    is_staff: bool = Field(default=False)
    is_superuser: bool = Field(default=False)
    is_active: bool = Field(default=True)
    first_name: str | None = Field(default=None, max_length=20, min_length=2)
    last_name: str | None = Field(default=None, max_length=20, min_length=2)
    profile_picture: str | None = Field(default=None)  
    phone: str | None = Field(default=None, max_length=20, min_length=8)
    role: Role = Field(default=Role.customer)
    agree_to_terms: bool = Field(default=False)
    password_hash: str = Field(default=None)

    todos: list["Todo"] = Relationship(back_populates="owner")

    def __repr__(self):
        return f"<User {self.username}>"

Description

unique=True, max_length=30, min_length=3 are not working in sqlmodel

Operating System

Windows

Operating System Details

No response

SQLModel Version

sqlmodel==0.0.22

Python Version

3.12

Additional Context

I am sorry if i didn't fill in the notes correctly. I am coming from django and currently learning about sqlmodel and fastapi. I love it! I think it is great, but i run into a few problems. I am coding along with one udemy course.

The author creates the database.py

from sqlmodel import SQLModel, create_engine, Field, Session

import models

sqlite_filename = 'database.db'

sqlite_url = f"sqlite:///{sqlite_filename}"

engine = create_engine(sqlite_url, echo=True)

if __name__ == '__main__':
    SQLModel.metadata.create_all(engine)

This is models.py

from sqlmodel import SQLModel, Field
from typing import Optional

class Category(SQLModel, table=True):
    id: Optional[int] = Field(primary_key=True, default=None)
    name: str = Field(index=True, unique=True, max_length=30, min_length=3)

This is main.py

from fastapi import FastAPI
from sqlmodel import SQLModel, Session
from models import Category, CreateCategory
from database import engine
from fastapi.responses import HTMLResponse

# define main app name
app = FastAPI()

# define database session name
session = Session(bind=engine)
@app.post('/category/create')
async def create_category(category:Category):
    new_category = Category(name=category.name)
    with Session(engine) as session:
        session.add(new_category)
        session.commit()
        session.refresh(new_category)
    return new_category

Now in the docs i saw that the version 0.0.7 has the unique validation working but i tried it and it doesn't, so i am sure the mistake is somewhere on my side.

So my code is the same. But i don't get validations for unique=True, max_length=30, min_length=3, and he does.

I also tried to create one model for creating the object, like this:

class CreateCategory(SQLModel):
    name: str = Field(unique=True, max_length=30, min_length=3, default='demo')

Then i use that in the async def with category:CreateCategory and now the min and max validations are working, but the unique=True still doesn't work.

So i am confused, i can't continue with the learning process until i learn this. If sqlmodel is to shorten the development time and act as a database model and validation model, why is there a need to create additional schemas for validation, especially if they are not working / not validating? Why can't we just use sqlalchemy and pydantic if there is a problem with sqlmodel?

Can someone please help explain this?

Thank you

p.s. in the field above, i wrote a User model based on my Django projects.

[YuriiMotov]

The fact that validation doesn't work for "table" models is a limitation of SQLModel, but it doesn't mean that it's useless.
It still helps avoid duplication (no need to duplicate fields):

class CategoryBase(SQLModel):
    name: str = Field(index=True, unique=True, max_length=30, min_length=3)

class Category(CategoryBase, table=True):
    id: Optional[int] = Field(primary_key=True, default=None)

class CreateCategory(CategoryBase):
    pass

The code example below works. It creates unique constraint, and it validates input values.

from typing import Optional

from fastapi import FastAPI
from sqlmodel import Field, Session, SQLModel, create_engine

class CategoryBase(SQLModel):
    name: str = Field(index=True, unique=True, max_length=30, min_length=3)

class Category(CategoryBase, table=True):
    id: Optional[int] = Field(primary_key=True, default=None)

class CreateCategory(CategoryBase):
    pass

sqlite_filename = 'database.db'

sqlite_url = f"sqlite:///{sqlite_filename}"

engine = create_engine(sqlite_url, echo=True)

SQLModel.metadata.create_all(engine)

# define main app name
app = FastAPI()

# define database session name
session = Session(bind=engine)

@app.post('/category/create')
async def create_category(category:CreateCategory):
    new_category = Category(name=category.name)
    with Session(engine) as session:
        session.add(new_category)
        session.commit()
        session.refresh(new_category)
    return new_category