How to query in SQLAlchemy[Asyncio] (Sanic)

Question

I am new to sanic and SQLAlchemy, I am implementing c2c ecom. I have a many-to-many relationship between orders and products that is joined by order_products table with quantity as an extra field on the join table (ie order_products)

class Order(Base):
    __tablename__ = "orders"
    uuid = Column(String(), primary_key=True)
    userId = Column(String(), nullable=False)
    status = Column(String(), nullable=False, default="draft")

    products = relationship(
        "Product", secondary="order_products", back_populates='orders')

    order_products = relationship(
        "OrderProduct", back_populates="order")

    def to_dict(self):
        return {"uuid": self.uuid, "userId": self.userId, "status": self.status, "products": [{
            "title": product.title,
            "price": product.price,
            "description": product.description,
            "uuid": product.uuid,
            "userId": product.userId,
            "quantity": product.order_products.quantity
        } for product in self.products]}

---

class Product(Base):
    __tablename__ = "products"
    uuid = Column(String(), primary_key=True)
    title = Column(String(), nullable=False)
    price = Column(FLOAT(), nullable=False)
    description = Column(String(), nullable=False)
    userId = Column(String(), nullable=False)

    orders = relationship(
        "Order", secondary="order_products", back_populates='products', uselist=False)

    order_products = relationship(
        "OrderProduct", back_populates="product")

---

class OrderProduct(Base):
    __tablename__ = "order_products"
    id = Column(Integer, primary_key=True)
    orderId = Column(String, ForeignKey("orders.uuid"))
    productId = Column(String, ForeignKey("products.uuid"))
    quantity = Column(Integer)

    # Define the relationships to the Order and Product tables
    order = relationship("Order", back_populates="order_products")
    product = relationship("Product", back_populates="order_products")

A user here is a buyer as well as seller.

I need to extract all the orders for a seller's product that is being paid for (ie Order.status == 'complete')and populate the products and quantity of those products.

[
    {
        "uuid": "order_Id_abc",
        "userId": "user_Id_def", ## USER who paid for the order
        "status": "complete",
        "products": [
            {
                "title": "One Piece t-shirt",
                "price": 900.0,
                "description": "Luffy at laugh tail island",
                "uuid": "product_Id",
                "userId": "current_user_Id", ## Sellers Id
                "quantity": 2
            },
         ## End up getting products of other Sellers, which was the part of this order.
        ]
    }
]

To achieve this I used following query

from sqlalchemy.orm import selectinload
from sqlalchemy.sql.expression import and_
from sqlalchemy.future import select

q = (select(Order)
         .join(OrderProduct, Order.uuid == OrderProduct.orderId)
         .join(Product, OrderProduct.productId == Product.uuid)
         .filter(and_((Order.status == 'complete'), (Product.userId == "current_user_id")))
         .options(selectinload(Order.products).selectinload(Product.order_products))
         .group_by(Order.uuid)
         )

I get my desired result, but end up getting other user's products too.

Can't figure out what is wrong here..

---

Thank you.

Answer 1

I was building query incorrectly. In order to filter the Products (or any entity) inside selectinload(), we can use and_ Comparator

https://docs.sqlalchemy.org/en/14/orm/internals.html#sqlalchemy.orm.RelationshipProperty.Comparator.and _

The correct query to achieve the desired result is:

q = (select(Order)
         .join(OrderProduct, Order.uuid == OrderProduct.orderId)
         .join(Product, OrderProduct.productId == Product.uuid)
         .filter(and_(Order.status == OrderStatus.Completed)
         .options(selectinload(Order.products.and_(Product.userId == "current_user_id"))
         .selectinload(Product.order_products))
         .group_by(Order.uuid)
         )

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Hope it helps... :)