feat: add filters (#357)

Co-authored-by: Paul Schweizer <paulschweizer@gmx.net>
Co-authored-by: Erik Wrede <erikwrede@users.noreply.github.com>

Author: 3 people

.gitignore

@@ -71,5 +71,8 @@ target/
 *.sqlite3
 .vscode
 
+# Schema
+*.gql
+
 # mypy cache
 .mypy_cache/

.pre-commit-config.yaml

@@ -1,5 +1,5 @@
 default_language_version:
-  python: python3.7
+  python: python3.8
 repos:
   - repo: https://github.com/pre-commit/pre-commit-hooks
     rev: v4.2.0
@@ -12,7 +12,7 @@ repos:
       - id: trailing-whitespace
         exclude: README.md
   - repo: https://github.com/pycqa/isort
-    rev: 5.10.1
+    rev: 5.12.0
     hooks:
       - id: isort
         name: isort (python)

docs/filters.rst

@@ -0,0 +1,213 @@
+=======
+Filters
+=======
+
+Starting in graphene-sqlalchemy version 3, the SQLAlchemyConnectionField class implements filtering by default. The query utilizes a ``filter`` keyword to specify a filter class that inherits from ``graphene.InputObjectType``.
+
+Migrating from graphene-sqlalchemy-filter
+---------------------------------------------
+
+If like many of us, you have been using |graphene-sqlalchemy-filter|_ to implement filters and would like to use the in-built mechanism here, there are a couple key differences to note. Mainly, in an effort to simplify the generated schema, filter keywords are nested under their respective fields instead of concatenated. For example, the filter partial ``{usernameIn: ["moderator", "cool guy"]}`` would be represented as ``{username: {in: ["moderator", "cool guy"]}}``.
+
+.. |graphene-sqlalchemy-filter| replace:: ``graphene-sqlalchemy-filter``
+.. _graphene-sqlalchemy-filter: https://github.com/art1415926535/graphene-sqlalchemy-filter
+
+Further, some of the constructs found in libraries like `DGraph's DQL <https://dgraph.io/docs/query-language/>`_ have been implemented, so if you have created custom implementations for these features, you may want to take a look at the examples below.
+
+
+Example model
+-------------
+
+Take as example a Pet model similar to that in the sorting example. We will use variations on this arrangement for the following examples.
+
+.. code::
+
+    class Pet(Base):
+        __tablename__ = 'pets'
+        id = Column(Integer(), primary_key=True)
+        name = Column(String(30))
+        age = Column(Integer())
+
+
+    class PetNode(SQLAlchemyObjectType):
+        class Meta:
+            model = Pet
+
+
+    class Query(graphene.ObjectType):
+        allPets = SQLAlchemyConnectionField(PetNode.connection)
+
+
+Simple filter example
+---------------------
+
+Filters are defined at the object level through the ``BaseTypeFilter`` class. The ``BaseType`` encompasses both Graphene ``ObjectType``\ s and ``Interface``\ s. Each ``BaseTypeFilter`` instance may define fields via ``FieldFilter`` and relationships via ``RelationshipFilter``. Here's a basic example querying a single field on the Pet model:
+
+.. code::
+
+    allPets(filter: {name: {eq: "Fido"}}){
+        edges {
+            node {
+                name
+            }
+        }
+    }
+
+This will return all pets with the name "Fido".
+
+
+Custom filter types
+-------------------
+
+If you'd like to implement custom behavior for filtering a field, you can do so by extending one of the base filter classes in ``graphene_sqlalchemy.filters``. For example, if you'd like to add a ``divisible_by`` keyword to filter the age attribute on the ``Pet`` model, you can do so as follows:
+
+.. code:: python
+
+    class MathFilter(FloatFilter):
+        class Meta:
+            graphene_type = graphene.Float
+
+        @classmethod
+        def divisible_by_filter(cls, query, field, val: int) -> bool:
+            return is_(field % val, 0)
+
+    class PetType(SQLAlchemyObjectType):
+        ...
+
+        age = ORMField(filter_type=MathFilter)
+
+    class Query(graphene.ObjectType):
+        pets = SQLAlchemyConnectionField(PetType.connection)
+
+
+Filtering over relationships with RelationshipFilter
+----------------------------------------------------
+
+When a filter class field refers to another object in a relationship, you may nest filters on relationship object attributes. This happens directly for 1:1 and m:1 relationships and through the ``contains`` and ``containsExactly`` keywords for 1:n and m:n relationships.
+
+
+:1 relationships
+^^^^^^^^^^^^^^^^
+
+When an object or interface defines a singular relationship, relationship object attributes may be filtered directly like so:
+
+Take the following SQLAlchemy model definition as an example:
+
+.. code:: python
+
+    class Pet
+        ...
+        person_id = Column(Integer(), ForeignKey("people.id"))
+
+    class Person
+        ...
+        pets = relationship("Pet", backref="person")
+
+
+Then, this query will return all pets whose person is named "Ada":
+
+.. code::
+
+    allPets(filter: {
+        person: {name: {eq: "Ada"}}
+    }) {
+        ...
+    }
+
+
+:n relationships
+^^^^^^^^^^^^^^^^
+
+However, for plural relationships, relationship object attributes must be filtered through either ``contains`` or ``containsExactly``:
+
+Now, using a many-to-many model definition:
+
+.. code:: python
+
+    people_pets_table = sqlalchemy.Table(
+        "people_pets",
+        Base.metadata,
+        Column("person_id", ForeignKey("people.id")),
+        Column("pet_id", ForeignKey("pets.id")),
+    )
+
+    class Pet
+        ...
+
+    class Person
+        ...
+        pets = relationship("Pet", backref="people")
+
+
+this query will return all pets which have a person named "Ben" in their ``people`` list.
+
+.. code::
+
+    allPets(filter: {
+        people: {
+            contains: [{name: {eq: "Ben"}}],
+        }
+    }) {
+        ...
+    }
+
+
+and this one will return all pets which hvae a person list that contains exactly the people "Ada" and "Ben" and no fewer or people with other names.
+
+.. code::
+
+    allPets(filter: {
+        articles: {
+            containsExactly: [
+                {name: {eq: "Ada"}},
+                {name: {eq: "Ben"}},
+            ],
+        }
+    }) {
+        ...
+    }
+
+And/Or Logic
+------------
+
+Filters can also be chained together logically using `and` and `or` keywords nested under `filter`. Clauses are passed directly to `sqlalchemy.and_` and `slqlalchemy.or_`, respectively. To return all pets named "Fido" or "Spot", use:
+
+
+.. code::
+
+    allPets(filter: {
+        or: [
+            {name: {eq: "Fido"}},
+            {name: {eq: "Spot"}},
+        ]
+    }) {
+        ...
+    }
+
+And to return all pets that are named "Fido" or are 5 years old and named "Spot", use:
+
+.. code::
+
+    allPets(filter: {
+        or: [
+            {name: {eq: "Fido"}},
+            { and: [
+                {name: {eq: "Spot"}},
+                {age: {eq: 5}}
+            }
+        ]
+    }) {
+        ...
+    }
+
+
+Hybrid Property support
+-----------------------
+
+Filtering over SQLAlchemy `hybrid properties <https://docs.sqlalchemy.org/en/20/orm/extensions/hybrid.html>`_ is fully supported.
+
+
+Reporting feedback and bugs
+---------------------------
+
+Filtering is a new feature to graphene-sqlalchemy, so please `post an issue on Github <https://github.com/graphql-python/graphene-sqlalchemy/issues>`_ if you run into any problems or have ideas on how to improve the implementation.

docs/index.rst

@@ -10,6 +10,7 @@ Contents:
    inheritance
    relay
    tips
+   filters
    examples
    tutorial
    api

examples/filters/README.md

@@ -0,0 +1,47 @@
+Example Filters Project
+================================
+
+This example highlights the ability to filter queries in graphene-sqlalchemy.
+
+The project contains two models, one named `Department` and another
+named `Employee`.
+
+Getting started
+---------------
+
+First you'll need to get the source of the project. Do this by cloning the
+whole Graphene-SQLAlchemy repository:
+
+```bash
+# Get the example project code
+git clone https://github.com/graphql-python/graphene-sqlalchemy.git
+cd graphene-sqlalchemy/examples/filters
+```
+
+It is recommended to create a virtual environment
+for this project. We'll do this using
+[virtualenv](http://docs.python-guide.org/en/latest/dev/virtualenvs/)
+to keep things simple,
+but you may also find something like
+[virtualenvwrapper](https://virtualenvwrapper.readthedocs.org/en/latest/)
+to be useful:
+
+```bash
+# Create a virtualenv in which we can install the dependencies
+virtualenv env
+source env/bin/activate
+```
+
+Install our dependencies:
+
+```bash
+pip install -r requirements.txt
+```
+
+The following command will setup the database, and start the server:
+
+```bash
+python app.py
+```
+
+Now head over to your favorite GraphQL client, POST to [http://127.0.0.1:5000/graphql](http://127.0.0.1:5000/graphql) and run some queries!

examples/filters/__init__.py

@@ -0,0 +1,16 @@
+from database import init_db
+from fastapi import FastAPI
+from schema import schema
+from starlette_graphene3 import GraphQLApp, make_playground_handler
+
+
+def create_app() -> FastAPI:
+    init_db()
+    app = FastAPI()
+
+    app.mount("/graphql", GraphQLApp(schema, on_get=make_playground_handler()))
+
+    return app
+
+
+app = create_app()

examples/filters/app.py

@@ -0,0 +1,49 @@
+from sqlalchemy import create_engine
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import sessionmaker
+
+Base = declarative_base()
+engine = create_engine(
+    "sqlite://", connect_args={"check_same_thread": False}, echo=True
+)
+session_factory = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+from sqlalchemy.orm import scoped_session as scoped_session_factory
+
+scoped_session = scoped_session_factory(session_factory)
+
+Base.query = scoped_session.query_property()
+Base.metadata.bind = engine
+
+
+def init_db():
+    from models import Person, Pet, Toy
+
+    Base.metadata.create_all()
+    scoped_session.execute("PRAGMA foreign_keys=on")
+    db = scoped_session()
+
+    person1 = Person(name="A")
+    person2 = Person(name="B")
+
+    pet1 = Pet(name="Spot")
+    pet2 = Pet(name="Milo")
+
+    toy1 = Toy(name="disc")
+    toy2 = Toy(name="ball")
+
+    person1.pet = pet1
+    person2.pet = pet2
+
+    pet1.toys.append(toy1)
+    pet2.toys.append(toy1)
+    pet2.toys.append(toy2)
+
+    db.add(person1)
+    db.add(person2)
+    db.add(pet1)
+    db.add(pet2)
+    db.add(toy1)
+    db.add(toy2)
+
+    db.commit()

examples/filters/database.py

@@ -0,0 +1,34 @@
+import sqlalchemy
+from database import Base
+from sqlalchemy import Column, ForeignKey, Integer, String
+from sqlalchemy.orm import relationship
+
+
+class Pet(Base):
+    __tablename__ = "pets"
+    id = Column(Integer(), primary_key=True)
+    name = Column(String(30))
+    age = Column(Integer())
+    person_id = Column(Integer(), ForeignKey("people.id"))
+
+
+class Person(Base):
+    __tablename__ = "people"
+    id = Column(Integer(), primary_key=True)
+    name = Column(String(100))
+    pets = relationship("Pet", backref="person")
+
+
+pets_toys_table = sqlalchemy.Table(
+    "pets_toys",
+    Base.metadata,
+    Column("pet_id", ForeignKey("pets.id")),
+    Column("toy_id", ForeignKey("toys.id")),
+)
+
+
+class Toy(Base):
+    __tablename__ = "toys"
+    id = Column(Integer(), primary_key=True)
+    name = Column(String(30))
+    pets = relationship("Pet", secondary=pets_toys_table, backref="toys")