Note: As of v1.3, only python 3.5+ is supported.
A pack of framework-agnostic, easy-to-integrate and well tested mixins for SQLAlchemy ORM.
Heavily inspired by Django ORM and Eloquent ORM
Why it's cool:
- framework-agnostic
- easy integration to your existing project:
from sqlalchemy_mixins import AllFeaturesMixin class User(Base, AllFeaturesMixin): pass
- clean code, splitted by modules
- follows best practices of Django ORM, Peewee and Eloquent ORM,
- 95%+ test coverage
- already powers a big project
Russian readers, see related article on habrahabr.ru
- Installation
- Quick Start
- Features
- Internal architecture notes
- Comparison with existing solutions
- Changelog
Use pip
pip install sqlalchemy_mixins
Run tests
python -m unittest discover sqlalchemy_mixins/
Here's a quick demo of what our mixins can do.
bob = User.create(name='Bob')
post1 = Post.create(body='Post 1', user=bob, rating=3)
post2 = Post.create(body='long-long-long-long-long body', rating=2,
user=User.create(name='Bill'),
comments=[Comment.create(body='cool!', user=bob)])
# filter using operators like 'in' and 'contains' and relations like 'user'
# will output this beauty: <Post #1 body:'Post1' user:'Bill'>
print(Post.where(rating__in=[2, 3, 4], user___name__like='%Bi%').all())
# joinedload post and user
print(Comment.with_joined(Comment.user, Comment.post).first())
# subqueryload posts
print(User.with_subquery(User.posts).first())
# sort by rating DESC, user name ASC
print(Post.sort('-rating', 'user___name').all())
# created_at, updated_at timestamps added automatically
print("Created Bob at ", bob.created_at)
# serialize to dict, with relationships
print(bob.to_dict(nested=True).all())
See full example
To interactively play with this example from CLI, install iPython and type
ipython -i examples\all_features.py
import sqlalchemy as sa
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy_mixins import AllFeaturesMixin
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite://'
db = SQLAlchemy(app)
######### Models #########
class BaseModel(db.Model, AllFeaturesMixin):
__abstract__ = True
pass
class User(BaseModel):
id = sa.Column(sa.Integer, primary_key=True)
name = sa.Column(sa.String)
######## Initialize ########
BaseModel.set_session(db.session)
######## Create test entity ########
db.create_all()
user = User.create(name='bob')
print(user)
This library relies on SQLAlchemy's autocommit
flag. It needs to be set to True when initializing the session i.e:
session = scoped_session(sessionmaker(bind=engine, autocommit=True))
BaseModel.set_session(session)
or with Flask-SQLAlchemy
db = SQLAlchemy(app, session_options={'autocommit': True})
Main features are
provided by ActiveRecordMixin
SQLAlchemy's Data Mapper pattern is cool, but Active Record pattern is easiest and more DRY.
Well, we implemented it on top of Data Mapper! All we need is to just inject session into ORM class while bootstrapping our app:
BaseModel.set_session(session)
# now we have access to BaseOrmModel.session property
We all love SQLAlchemy, but doing CRUD is a bit tricky there.
For example, creating an object needs 3 lines of code:
bob = User(name='Bobby', age=1)
session.add(bob)
session.flush()
Well, having access to session from model, we can just write
bob = User.create(name='Bobby', age=1)
that's how it's done in Django ORM and Peewee
update and delete methods are provided as well
bob.update(name='Bob', age=21)
bob.delete()
And, as in Django and Eloquent, we can quickly retrieve object by id
User.find(1) # instead of session.query(User).get(1)
and fail if such id doesn't exist
User.find_or_fail(123987) # will raise sqlalchemy_mixins.ModelNotFoundError
See full example and tests
As in Flask-SQLAlchemy, Peewee and Django ORM, you can quickly query some class
User.query # instead of session.query(User)
Also we can quickly retrieve first or all objects:
User.first() # instead of session.query(User).first()
User.all() # instead of session.query(User).all()
See full example and tests
provided by EagerLoadMixin
If you use SQLAlchemy's eager loading, you may find it not very convenient, especially when we want, say, load user, all his posts and comments to every his post in the same query.
Well, now you can easily set what ORM relations you want to eager load
User.with_({
User.posts: {
Post.comments: {
Comment.user: JOINED
}
}
}).all()
Sometimes we want to load relations in separate query, i.e. do subqueryload. For example, we load posts on page like this, and for each post we want to have user and all comments (and comment authors).
To speed up query, we load comments in separate query, but, in this separate query, join user
from sqlalchemy_mixins import JOINED, SUBQUERY
Post.with_({
Post.user: JOINED, # joinedload user
Post.comments: (SUBQUERY, { # load comments in separate query
Comment.user: JOINED # but, in this separate query, join user
})
}).all()
Here, posts will be loaded on first query, and comments with users - in second one. See SQLAlchemy docs for explaining relationship loading techniques.
For simple cases, when you want to just joinedload or subqueryload a few relations, we have easier syntax for you:
Comment.with_joined(Comment.user, Comment.post).first()
User.with_subquery(User.posts).all()
See full example and tests
provided by SmartQueryMixin
We implement Django-like field lookups and automatic relation joins.
It means you can filter and sort dynamically by attributes defined in strings!
So, having defined Post
model with Post.user
relationship to User
model,
you can write
Post.where(rating__gt=2, user___name__like='%Bi%').all() # post rating > 2 and post user name like ...
Post.sort('-rating', 'user___name').all() # sort by rating DESC, user name ASC
(___
splits relation and attribute, __
splits attribute and operator)
If you need more flexibility, you can use low-level
filter_expr
methodsession.query(Post).filter(*Post.filter_expr(rating__gt=2, body='text'))
, see example.It's like
filter_by
in SQLALchemy, but also allows magic operators likerating__gt
.Note:
filter_expr
method is very low-level and does NOT do magic Django-like joins. Usesmart_query
for that.
All relations used in filtering/sorting should be explicitly set, not just being a backref
In our example,
Post.user
relationship should be defined inPost
class even ifUser.posts
is defined too.So, you can't type
class User(BaseModel): # ... user = sa.orm.relationship('User', backref='posts')and skip defining
Post.user
relationship. You must define it anyway:class Post(BaseModel): # ... user = sa.orm.relationship('User') # define it anyway
For DRY-ifying your code and incapsulating business logic, you can use SQLAlchemy's hybrid attributes and hybrid_methods. Using them in our filtering/sorting is straightforward (see examples and tests).
See full example and tests
Well, as SmartQueryMixin
does auto-joins for filtering/sorting,
there's a sense to tell sqlalchemy that we already joined that relation.
So that relations are automatically set to be joinedload if they were used for filtering/sorting.
So, if we write
comments = Comment.where(post___public=True, post___user___name__like='Bi%').all()
then no additional query will be executed if we will access used relations
comments[0].post
comments[0].post.user
Cool, isn't it? =)
See full example and tests
provided by SmartQueryMixin
In real world, we want to filter, sort and also eager load some relations at once.
Well, if we use the same, say, User.posts
relation in filtering and sorting,
it should not be joined twice.
That's why we combined filter, sort and eager load in one smartest method:
Comment.smart_query(
filters={
'post___public': True,
'user__isnull': False
},
sort_attrs=['user___name', '-created_at'],
schema={
Comment.post: {
Post.user: JOINED
}
}).all()
** New in 0.2.3 ** In real world, you may need to "smartly" apply filters/sort/eagerload to any arbitrary query. And you can do this with standalone
smart_query
function:smart_query(any_query, filters=...)It's especially useful for filtering/sorting/eagerloading relations with lazy='dynamic' for pages like this:
smart_query(user.comments_, filters=...)See this example
** Experimental ** Additional logic (OR, AND, NOT etc) can be expressed using a nested structure for filters, with sqlalchemy operators (or any callable) as keys:
from sqlalchemy import or_ Comment.smart_query(filters={ or_: { 'post___public': True, 'user__isnull': False }})
See this example for more details
See full example and tests
provided by ReprMixin
As developers, we need to debug things with convenience. When we play in REPL, we can see this
>>> session.query(Post).all()
[<myapp.models.Post object at 0x04287A50>, <myapp.models.Post object at 0x04287A90>]
Well, using our mixin, we can have more readable output with post IDs:
>>> session.query(Post).all()
[<Post #11>, <Post #12>]
Even more, in Post
model, we can define what else (except id) we want to see:
class User(BaseModel):
__repr_attrs__ = ['name']
# ...
class Post(BaseModel):
__repr_attrs__ = ['user', 'body'] # body is just column, user is relationship
# ...
Now we have
>>> session.query(Post).all()
[<Post #11 user:<User #1 'Bill'> body:'post 11'>,
<Post #12 user:<User #2 'Bob'> body:'post 12'>]
Long attributes will be cut:
long_post = Post(body='Post 2 long-long body', user=bob)
>>> long_post
<Post #2 body:'Post 2 long-lon...' user:<User #1 'Bob'>>
And you can customize max __repr__
length:
class Post(BaseModel):
# ...
__repr_max_length__ = 25
# ...
>>> long_post
<Post #2 body:'Post 2 long-long body' user:<User #1 'Bob'>>
See full example and tests
provided by SerializeMixin
You can convert your model to dict.
# 1. Without relationships
#
# {'id': 1, 'name': 'Bob'}
print(user.to_dict())
# 2. With relationships
#
# {'id': 1,
# 'name': 'Bob',
# 'posts': [{'body': 'Post 1', 'id': 1, 'user_id': 1},
# {'body': 'Post 2', 'id': 2, 'user_id': 1}]}
print(user.to_dict(nested=True))
See full example
provided by TimestampsMixin
You can view the created and updated timestamps.
bob = User(name="Bob")
session.add(bob)
session.flush()
print("Created Bob: ", bob.created_at)
# Created Bob: 2019-03-04 03:53:53.606765
print("Pre-update Bob: ", bob.updated_at)
# Pre-update Bob: 2019-03-04 03:53:53.606769
time.sleep(2)
bob.name = "Robert"
session.commit()
print("Updated Bob: ", bob.updated_at)
# Updated Bob: 2019-03-04 03:53:58.613044
See full example
Some mixins re-use the same functionality. It lives in SessionMixin
(session access) and InspectionMixin
(inspecting columns, relations etc.) and other mixins inherit them.
You can use these mixins standalone if you want.
There're a lot of extensions for SQLAlchemy, but most of them are not so universal.
We found several implementations of this pattern.
Cool, but it forces you to use their own way to instantiate SQLAlchemy
while to use ActiveRecordMixin
you should just make you model to inherit it.
Cool, but tightly coupled with Flask.
Framework-agnostic, but lacks of functionality (only save
method is provided) and Readme.
There exists sqlalchemy-django-query package which does similar things and it's really awesome.
But:
- it doesn't automatic eager load relations
- it doesn't work with hybrid attributes and hybrid_methods
sqlalchemy-repr already does this, but there you can't choose which columns to output. It simply prints all columns, which can lead to too big output.
More clear methods in EagerLoadMixin
:
-
added
with_subquery
method: it's likewith_joined
, but for subqueryload. So you can now write:User.with_subquery('posts', 'comments').all()
-
with_joined
method arguments change: instead ofComment.with_joined(['user','post'])
now simply write
Comment.with_joined('user','post')
-
with_
method arguments change: it now accepts only dict schemas. If you want to quickly joinedload relations, usewith_joined
-
with_dict
method removed. Instead, usewith_
method
Other changes in EagerLoadMixin
:
-
constants rename: use cleaner
JOINED
andSUBQUERY
instead ofJOINEDLOAD
andSUBQUERYLOAD
-
do not allow
None
in schema anymore, so instead ofComment.with_({'user': None})
write
Comment.with_({'user': JOINED})
Fix in InspectionMixin.columns
property.
It didn't return columns inherited from other class. Now it works correct:
class Parent(BaseModel):
__tablename__ = 'parent'
id = sa.Column(sa.Integer, primary_key=True)
class Child(Parent):
some_prop = sa.Column(sa.String)
Child.columns # before it returned ['some_prop']
# now it returns ['id', 'some_prop']
Fixed bug in ReprMixin
: it crashed for objects without ID (newly created ones, not added yet to the session).
SmartQueryMixin
: decoupled smart_query
function from ORM classes
so now you can use it with any query like
smart_query(any_query, filters=...)
See description (at the end of paragraph) and example
-
Added SerializationMixin (thanks, jonatasleon)
-
Added
ne
operator (thanks, https://github.com/sophalch), so now you can write something like
Post.where(rating__ne=2).all()
This version contains breaking change, reverted in v1.2.1. So:
- v1.2 was removed from PyPi to avoid confusions
- for those who already downloaded v1.2, we hardly recommend to switch to 1.2.1.
Just use v1.2.1 instead
By mistake, v1.2 code was released on PyPi as v1.1. It has been deleted from PyPi to avoid confusion. Sorry for any inconvenience guys.
-
Removed Python 2, Python 3.2 compatibility.
-
Added Python 3.7, 3.8 compatibility.
-
Added TimestampsMixin (thanks, jonatasleon).
-
(Breaking change, fixed in v1.2.1) TimestampsMixin was included it to AllFeaturesMixin which means
created_at
andupdated_at
fields were added to all models usingAllFeaturesMixin
which means you need to write migrations adding these fields. -
Added
contains
operator (thanks, alexbredo). -
Added date comparison operators (thanks, proteusvacuum), so now you can write something like
Post.where(created_at__year_ge=2014).all()
Post.where(created_at__month_gt=10).all()
Post.where(created_at__day_le=30).all()
Reverted breaking change introduced in 1.2:
removed TimestampsMixin from AllFeaturesMixin. This addition in v1.2 forced package users to write and run migration to add created_at
and updated_at
fields to all tables whose ORM models used AllFeaturesMixin
.
Now you should add TimestampsMixin
separately:
class BaseModel(Base, AllFeaturesMixin, TimestampsMixin):
# ...
Add support for SQLAlchemy 1.4
This version contains breaking changes in multiple methods i.e methods that simplify eager loading. The use of strings while eager loading has been removed completely in SQLAlchemy 2.0. To much this behaviour, we have also removed the use of strings when eager loading
- Migrate to SQLAlchemy 2.0
- All methods in the
EagerLoadMixin
no longer accept strings. Note This means that you can only pass direct relationships. - The
schema
parameter of thesmart_query
method/function no longer accepts string keys. - Dropped Python 3.6
- Add Python 3.10 compatibility