Issue with created_at timestamp field not being correctly created in schema with default_factory. How do i add timestamp as a column in table in SQLmodel ?

[srikrishnasajjarao]

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Example Code

class Job(SQLModel, table=True):
    id: str = Field(default_factory=lambda: str(uuid.uuid4()), primary_key=True)
    user_id: str
    created_at: datetime = Field(default_factory=datetime.utcnow)

Description

Problem

When defining a model with a created_at field using Field(default_factory=datetime.utcnow) in SQLModel, the created_at field is not being created as a timestamp column in the database schema.

Steps to Reproduce

1. Define a model with a created_at field using Field(default_factory=datetime.utcnow).
2. Create the table using SQLModel.metadata.create_all(engine).
3. Add a record to the table without explicitly setting created_at.
4. Observe that the created_at field is not correctly set in the database schema.

Expected Behavior

The created_at field should be automatically created as a timestamp column in the database, and when a new record is created, the field should be populated with the current UTC timestamp.

Environment

• SQLModel version: [version]
• Database: [SQLite/PostgreSQL/MySQL]
• Python version: [version]

Additional Information

It seems like the field is not automatically treated as a timestamp column in the database when using default_factory=datetime.utcnow. This issue should be addressed to ensure the field is correctly handled both in the model and the database schema.

Possible Fix

One solution could be to add support for automatic timestamp handling at the database level or update the documentation for users to handle this behavior manually.

Operating System

Windows

Operating System Details

No response

SQLModel Version

0.0.22

Python Version

3.10.16

Additional Context

No response

[YuriiMotov]

Can't reproduce the issue (see details)

Details

import uuid
from datetime import datetime

from sqlmodel import Field, SQLModel, create_engine


class Job(SQLModel, table=True):
    id: str = Field(default_factory=lambda: str(uuid.uuid4()), primary_key=True)
    user_id: str
    created_at: datetime = Field(default_factory=datetime.utcnow)


engine = create_engine(
    "postgresql://user:mysecretpassword@localhost/some_db", echo=True
)
SQLModel.metadata.drop_all(engine)
SQLModel.metadata.create_all(engine)

CREATE TABLE job (
        id VARCHAR NOT NULL, 
        user_id VARCHAR NOT NULL, 
        created_at TIMESTAMP WITHOUT TIME ZONE NOT NULL, 
        PRIMARY KEY (id)
)

To specify server-side logic, you should specify server_default via sa_column_kwargs:

import uuid
from datetime import datetime

from sqlmodel import Field, SQLModel, create_engine, func

class Job(SQLModel, table=True):
    id: str = Field(default_factory=lambda: str(uuid.uuid4()), primary_key=True)
    user_id: str
    created_at: datetime = Field(
        sa_column_kwargs={
            'server_default': func.now(),
        },
    )

engine = create_engine(
    "postgresql://user:mysecretpassword@localhost/some_db", echo=True
)
SQLModel.metadata.drop_all(engine)
SQLModel.metadata.create_all(engine)

CREATE TABLE job (
        id VARCHAR NOT NULL, 
        user_id VARCHAR NOT NULL, 
        created_at TIMESTAMP WITHOUT TIME ZONE DEFAULT now() NOT NULL, 
        PRIMARY KEY (id)
)