Default values for fields not working as expected with SQLModel in PostgreSQL

[Yoosuph]

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Issue Content

I'm encountering an issue where default values for fields in my SQLModel class are not being applied when using PostgreSQL. Despite specifying default or default_factory for various fields, the database does not seem to handle these defaults, and errors occur during table creation or insertion.

from datetime import datetime
from sqlmodel import Field, SQLModel
from typing import Optional

class Posts(SQLModel, table=True):
    id: Optional[int] = Field(default_factory=int, primary_key=True)
    title: str
    content: str
    published: Optional[bool] = Field(default_factory=lambda: True)
    created_at: Optional[datetime] = Field(default_factory=datetime.now)

[ArazHeydarov]

default and default_factory arguments are only Python-level defaults. They'll assign a default value to your field only during the creation of instances in Python.

post = Posts(title="Some title", content="Some Content")
assert post.id == 0

If you go directly to the Postgres DB and try to add a row there, these defaults won't be considered.
In order to enforce the default in DB level, you can use sa_column_kwargs={"server_default": "<value>"} argument.
I hope this will solve your issue.