starter.rst

Getting Started

Welcome to the graphene-sqlalchemy documentation! Graphene is a powerful Python library for building GraphQL APIs, and SQLAlchemy is a popular ORM (Object-Relational Mapping) tool for working with databases. When combined, graphene-sqlalchemy allows developers to quickly and easily create a GraphQL API that seamlessly interacts with a SQLAlchemy-managed database. It is fully compatible with SQLAlchemy 1.4 and 2.0. This documentation provides detailed instructions on how to get started with graphene-sqlalchemy, including installation, setup, and usage examples.

Installation

To install graphene-sqlalchemy, just run this command in your shell:

pip install --pre "graphene-sqlalchemy"

Examples

Here is a simple SQLAlchemy model:

from sqlalchemy import Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

class UserModel(Base):
    __tablename__ = 'user'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    last_name = Column(String)

To create a GraphQL schema for it, you simply have to write the following:

import graphene
from graphene_sqlalchemy import SQLAlchemyObjectType

class User(SQLAlchemyObjectType):
    class Meta:
        model = UserModel
        # use `only_fields` to only expose specific fields ie "name"
        # only_fields = ("name",)
        # use `exclude_fields` to exclude specific fields ie "last_name"
        # exclude_fields = ("last_name",)

class Query(graphene.ObjectType):
    users = graphene.List(User)

    def resolve_users(self, info):
        query = User.get_query(info)  # SQLAlchemy query
        return query.all()

schema = graphene.Schema(query=Query)

Then you can simply query the schema:

query = '''
    query {
      users {
        name,
        lastName
      }
    }
'''
result = schema.execute(query, context_value={'session': db_session})

It is important to provide a session for graphene-sqlalchemy to resolve the models. In this example, it is provided using the GraphQL context. See :doc:`tips` for other ways to implement this.

You may also subclass SQLAlchemyObjectType by providing abstract = True in your subclasses Meta:

from graphene_sqlalchemy import SQLAlchemyObjectType

class ActiveSQLAlchemyObjectType(SQLAlchemyObjectType):
    class Meta:
        abstract = True

    @classmethod
    def get_node(cls, info, id):
        return cls.get_query(info).filter(
            and_(cls._meta.model.deleted_at==None,
                 cls._meta.model.id==id)
            ).first()

class User(ActiveSQLAlchemyObjectType):
    class Meta:
        model = UserModel

class Query(graphene.ObjectType):
    users = graphene.List(User)

    def resolve_users(self, info):
        query = User.get_query(info)  # SQLAlchemy query
        return query.all()

schema = graphene.Schema(query=Query)

More complex inhertiance using SQLAlchemy's polymorphic models is also supported. You can check out :doc:`inheritance` for a guide.