Selecting an item by its associated tables - flask

Question

I'm working on building a recipe database. I'm trying to build a query wehere I get all recipies that include a certain ingredient (such as onions, carrots), but I'm not how build my query. Essentally I'm trying to get a list of recipies that (given the proper amount of joins) have an Ingredient.name = 'onion'. My models are as follows:
ingredients = db.Table('ingredients',
db.Column('modified_ingredient', db.Integer, db.ForeignKey('modified_ingredient.id')),
db.Column('ingredient', db.Integer, db.ForeignKey('ingredient.id'))
)
modifiers = db.Table('modifiers',
db.Column('modified_ingredient', db.Integer, db.ForeignKey('modified_ingredient.id')),
db.Column('modifier', db.Integer, db.ForeignKey('modifier.id'))
)
modified_ingredients = db.Table('modified_ingredients',
db.Column('recipe', db.Integer, db.ForeignKey('recipe.id')),
db.Column('modified_ingredient', db.Integer, db.ForeignKey('modified_ingredient.id'))
)
class Recipe(db.Model):
__tablename__ = 'recipe'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(256))
description = db.Column(db.Text)
directions = db.Column(db.Text)
prep_time = db.Column(db.Integer)
cook_time = db.Column(db.Integer)
image = db.Column(db.LargeBinary())
ingredients = db.relationship('ModifiedIngredient', secondary=modified_ingredients)
class Ingredient(db.Model):
__tablename__ = 'ingredient'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(30), index=True, unique=True)
class Modifier(db.Model):
__tablename__ = 'modifier'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(30), index=True, unique=True)
class ModifiedIngredient(db.Model):
__tablename__ = 'modified_ingredient'
id = db.Column(db.Integer, primary_key=True)
amount = db.Column(db.Integer)
unit = db.Column(db.String(20))
ingredients = db.relationship('Ingredient', secondary=ingredients,
backref=db.backref('ingredients', lazy='dynamic'), lazy='dynamic')
modifiers = db.relationship('Modifier', secondary=modifiers,
backref=db.backref('modifiers', lazy='dynamic'), lazy='dynamic')
It's mostly my inexperience with SQL and SQLAlchemy that is stumping me. I know that I'm joining something, but I'm not exactly sure how to phrase it in a way that works.

Answer 1

Option-1: very tidy, but might not be the most efficient due to nested EXISTS clause:
q = (db.session.query(Recipe)
.filter(Recipe.ingredients.any(
ModifiedIngredient.ingredients.any(
Ingredient.name == 'onion')
)))
Option-2: should be faster, but if you query only certain columns (use query(Recipe.name, ..) instead of whole objects as below), you will end with with multiple results per each Recipe row because of JOINs:
q = (db.session.query(Recipe)
.join(Recipe.ingredients)
.join(Ingredient, ModifiedIngredient.ingredients)
.filter(Ingredient.name == 'onion')
)