ActiveModel: ORM Wrapper for SQLModel

No, this isn't really ActiveModel. It's just a wrapper around SQLModel that provides a more ActiveRecord-like interface.

SQLModel is not an ORM. It's a SQL query builder and a schema definition tool.

This package provides a thin wrapper around SQLModel that provides a more ActiveRecord-like interface with things like:

• Timestamp column mixins
• Lifecycle hooks

Getting Started

First, setup your DB:

Then, setup some models:

from activemodel import BaseModel
from activemodel.mixins import TimestampsMixin, TypeIDMixin

class User(
    BaseModel,
    # optionally, obviously
    TimestampsMixin,
    # you can use a different pk type, but why would you?
    # put this mixin last otherwise `id` will not be the first column in the DB
    TypeIDMixin("user"),
    # wire this model into the DB, without this alembic will not generate a migration
    table=True
):
    a_field: str

Usage

Integrating Alembic

alembic init will not work out of the box. You need to mutate a handful of files:

• To import all of your models you want in your DB. Here's my recommended way to do this.
• Use your DB URL from the ENV
• Target sqlalchemy metadata to the sqlmodel-generated metadata
• Most likely you'll want to add alembic-postgresql-enum so migrations work properly

Take a look at these scripts for an example of how to fully integrate Alembic into your development workflow.

Here's a diff from the bare alembic init from version 1.14.1.

diff --git i/test/migrations/alembic.ini w/test/migrations/alembic.ini
index 0d07420..a63631c 100644
--- i/test/migrations/alembic.ini
+++ w/test/migrations/alembic.ini
@@ -3,13 +3,14 @@
 [alembic]
 # path to migration scripts
 # Use forward slashes (/) also on windows to provide an os agnostic path
-script_location = .
+script_location = migrations
 
 # template used to generate migration file names; The default value is %%(rev)s_%%(slug)s
 # Uncomment the line below if you want the files to be prepended with date and time
 # see https://alembic.sqlalchemy.org/en/latest/tutorial.html#editing-the-ini-file
 # for all available tokens
 # file_template = %%(year)d_%%(month).2d_%%(day).2d_%%(hour).2d%%(minute).2d-%%(rev)s_%%(slug)s
+file_template = %%(year)d_%%(month).2d_%%(day).2d_%%(rev)s_%%(slug)s
 
 # sys.path path, will be prepended to sys.path if present.
 # defaults to the current working directory.
diff --git i/test/migrations/env.py w/test/migrations/env.py
index 36112a3..a1e15c2 100644
--- i/test/migrations/env.py
+++ w/test/migrations/env.py
@@ -1,3 +1,6 @@
+# fmt: off
+# isort: off
+
 from logging.config import fileConfig
 
 from sqlalchemy import engine_from_config
@@ -14,11 +17,17 @@ config = context.config
 if config.config_file_name is not None:
     fileConfig(config.config_file_name)
 
+from sqlmodel import SQLModel
+from test.models import *
+from test.utils import database_url
+
+config.set_main_option("sqlalchemy.url", database_url())
+
 # add your model's MetaData object here
 # for 'autogenerate' support
 # from myapp import mymodel
 # target_metadata = mymodel.Base.metadata
-target_metadata = None
+target_metadata = SQLModel.metadata
 
 # other values from the config, defined by the needs of env.py,
 # can be acquired:
diff --git i/test/migrations/script.py.mako w/test/migrations/script.py.mako
index fbc4b07..9dc78bb 100644
--- i/test/migrations/script.py.mako
+++ w/test/migrations/script.py.mako
@@ -9,6 +9,8 @@ from typing import Sequence, Union
 
 from alembic import op
 import sqlalchemy as sa
+import sqlmodel
+import activemodel
 ${imports if imports else ""}
 
 # revision identifiers, used by Alembic.

Here are some useful resources around Alembic + SQLModel:

• fastapi/sqlmodel#85
• https://testdriven.io/blog/fastapi-sqlmodel/

Query Wrapper

This tool is added to all BaseModels and makes it easy to write SQL queries. Some examples:

Easy Database Sessions

I hate the idea f

• Behavior should be intuitive and easy to understand. If you run save(), it should save, not stick the save in a transaction.
• Don't worry about dead sessions. This makes it easy to lazy-load computed properties and largely eliminates the need to think about database sessions.

There are a couple of thorny problems we need to solve for here:

• In-memory fastapi servers are not the same as a uvicorn server, which is threaded and uses some sort of threadpool model for handling async requests. I don't claim to understand the entire implementation. For global DB session state (a) we can't use global variables (b) we can't use thread-local variables.

https://github.com/tomwojcik/starlette-context

Example Queries

• Conditional: Scrape.select().where(Scrape.id < last_scraped.id).all()
• Equality: MenuItem.select().where(MenuItem.menu_id == menu.id).all()
• IN example: CanonicalMenuItem.select().where(col(CanonicalMenuItem.id).in_(canonized_ids)).all()
• Compound where query: User.where((User.last_active_at != None) & (User.last_active_at > last_24_hours)).count()

TypeID

I'm a massive fan of Stripe-style prefixed UUIDs. There's an excellent project that defined a clear spec for these IDs. I've used the python implementation of this spec and developed a clean integration with SQLModel that plays well with fastapi as well.

Here's an example of defining a relationship:

import uuid

from activemodel import BaseModel
from activemodel.mixins import TimestampsMixin, TypeIDMixin
from activemodel.types import TypeIDType
from sqlmodel import Field, Relationship

from .patient import Patient

class Appointment(
    BaseModel,
    # this adds an `id` field to the model with the correct type
    TypeIDMixin("appointment"),
    table=True
):
    # `foreign_key` is a activemodel-specific method to generate the right `Field` for the relationship
    # TypeIDType is really important here for fastapi serialization
    doctor_id: TypeIDType = Doctor.foreign_key()
    doctor: Doctor = Relationship()

Limitations

Validation

SQLModel does not currently support pydantic validations (when table=True). This is very surprising, but is actually the intended functionality:

• fastapi/sqlmodel#897
• fastapi/sqlmodel#1041
• fastapi/sqlmodel#453
• fastapi/sqlmodel#52 (comment)

For validation:

• When consuming API data, use a separate shadow model to validate the data with table=False and then inherit from that model in a model with table=True.
• When validating ORM data, use SQL Alchemy hooks.

Related Projects

• https://github.com/woofz/sqlmodel-basecrud
• https://github.com/0xthiagomartins/sqlmodel-controller

Inspiration

• https://github.com/peterdresslar/fastapi-sqlmodel-alembic-pg
• Albemic instructions
• https://github.com/fastapiutils/fastapi-utils/
• https://github.com/fastapi/full-stack-fastapi-template
• https://github.com/DarylStark/my_data/
• https://github.com/petrgazarov/FastAPI-app/tree/main/fastapi_app