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The missing SQLAlchemy ORM service layer

Project description

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The missing SQLAlchemy ORM service layer.

Introduction

So what exactly is sqlservice and what does “the missing SQLAlchemy ORM service layer” even mean? The “service layer” in this context is that part of your application that forms your core domain logic. This is where your ORM models meet your database session and all the magic happens.

Features

This library is meant to enhanced your usage of SQLAlchemy. SQLAlchemy is great and this library tries to build upon that by providing useful abstractions on top of it.

  • Database client similar to Flask-SQLAlchemy and alchy.DatabaseManager that helps manage an ORM scoped session.
  • Base class for a declarative ORM Model that makes updating model columns and relationships easier and convert to a dictionary a breeze.
  • A decorator based event registration for SQLAlchemy ORM events that can be used at the model class level. No need to register the event handler outside of the class definition.
  • A base service class that provides a unified way to save database records as either ORM models or plain dictionaries.
  • An application-side nestable transaction context-manager that helps implement pseudo-subtransactions for those that want implicit transaction demarcation, i.e. autocommit=False, without the use of subtransactions=True.
  • And more!

History

This library’s direct predecessor is alchy which itself started as a drop-in replacement for Flask-SQLAlchemy combined with new functionality centering around the “fat-model” style. This library takes a different approach and encourages a “fat-service” style. As such, it is primarily a rewrite of alchy with some of its features ported over and improved, some of its features removed, and other features added. With alchy, one’s primary interface with the database was through a model class. Whereas with sqlservice, one’s primary interface with the database is through a service class.

Requirements

Quickstart

First, install using pip:

pip install sqlservice

Then, define some ORM models:

import re

from sqlalchemy import Column, ForeignKey, orm, types

from sqlservice import ModelBase, declarative_base, event


Model = declarative_base(ModelBase)

class User(Model):
    __tablename__ = 'user'

    id = Column(types.Integer(), primary_key=True)
    name = Column(types.String(100))
    email = Column(types.String(100))
    phone = Column(types.String(10))

    roles = orm.relation('UserRole')

    @event.on_set('phone', retval=True)
    def on_set_phone(self, value, oldvalue, initator):
        # Strip non-numeric characters from phone number.
        return re.sub('[^0-9]', '', value)

class UserRole(Model):
    __tablename__ = 'user_role'

    id = Column(types.Integer(), primary_key=True)
    user_id = Column(types.Integer(), ForeignKey('user.id'), nullable=False)
    role = Column(types.String(25), nullable=False)

Next, configure a database client:

from sqlservice import SQLClient

config = {
    'SQL_DATABASE_URI': 'sqlite:///db.sql',
    'SQL_ECHO': True,
    'SQL_POOL_SIZE': 5,
    'SQL_POOL_TIMEOUT': 30,
    'SQL_POOL_RECYCLE': 3600,
    'SQL_MAX_OVERFLOW': 10,
    'SQL_AUTOCOMMIT': False,
    'SQL_AUTOFLUSH': True
}

db = SQLClient(config, Model=Model)

Create a service class for our models:

from sqlservice import SQLService


class UserService(SQLService):
    model_class = User

Prepare the database by creating all tables:

db.create_all()

Finally (whew!), start interacting with the database:

user_service = UserService(db)

# Insert a new record in the database.
data = {'name': 'Jenny', 'email': 'jenny@example.com', 'phone': '555-867-5309'}
user = user_service.save(data)


# Fetch records.
assert user is user_service.get(data.id)
assert user is user_service.find_one(id=user.id)
assert user is user_service.find(User.id == user.id)[0]

# Serialize to a dict.
assert user.to_dict() == {'id': 1,
                          'name': 'Jenny',
                          'email': 'jenny@example.com',
                          'phone': '5558675309'}

assert dict(user) == user.to_dict()

# Update the record and save.
user.phone = '222-867-5309'
user_service.save(user)

# Upsert on primary key automatically.
assert user is user_service({'id': 1,
                             'name': 'Jenny',
                             'email': 'jenny@example.com',
                             'phone': '5558675309'})

# Delete the model.
user_service.delete(user)
# OR user_service.delete([user])
# OR user_service.delete(user.id)
# OR user_service.delete(dict(user))

For more details, please see the full documentation at http://sqlservice.readthedocs.org.

Changelog

v0.1.0 (2016-05-24)

  • First release.

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