Async ORM operations in Django - Mini Project: Build & Apply

Async ORM operations

📖 Scenario: You are building a simple Django app to manage books in a library. You want to use asynchronous database operations to improve performance when fetching and filtering books.

🎯 Goal: Learn how to perform asynchronous ORM operations in Django by creating a model, setting up a filter condition, querying the database asynchronously, and returning the results.

📋 What You'll Learn

Create a Django model called Book with fields title (CharField) and pages (IntegerField).

Define a variable min_pages to set the minimum number of pages for filtering books.

Use asynchronous ORM methods to get all books with pages greater than or equal to min_pages.

Return the filtered books asynchronously in a function.

💡 Why This Matters

🌍 Real World

Async ORM operations help improve performance in web apps by not blocking the server while waiting for database queries.

💼 Career

Many modern Django projects use async views and ORM calls to handle high traffic efficiently, making async ORM skills valuable for backend developers.

1

Create the Book model

Create a Django model called Book with a title field as CharField(max_length=100) and a pages field as IntegerField() inside models.py.

Django

from django.db import models

# Define the Book model with title and pages fields
# Your code here

Hint

Use class Book(models.Model): and define the fields as instructed.

2

Set the minimum pages filter

In a new file or the same file, create a variable called min_pages and set it to 100 to use as a filter threshold.

Django

from django.db import models

class Book(models.Model):
    title = models.CharField(max_length=100)
    pages = models.IntegerField()

# Set the minimum pages filter
# Your code here

Hint

Just create a variable min_pages and assign it the value 100.

3

Query books asynchronously

Write an asynchronous function called get_books_async that uses Django's async ORM method afilter with pages__gte=min_pages to get all books with pages greater than or equal to min_pages. Use an async list comprehension to get the results.

Django

from django.db import models

class Book(models.Model):
    title = models.CharField(max_length=100)
    pages = models.IntegerField()

min_pages = 100

# Define async function to get filtered books
# Your code here

Hint

Define an async function and use [book async for book in Book.objects.filter(pages__gte=min_pages).aiterator()].

4

Complete async ORM operation

Add a final line to call get_books_async inside an async context or view to complete the async ORM operation setup.

Django

from django.db import models

class Book(models.Model):
    title = models.CharField(max_length=100)
    pages = models.IntegerField()

min_pages = 100

async def get_books_async():
    books = [book async for book in Book.objects.filter(pages__gte=min_pages).aiterator()]
    return books

# Call get_books_async in an async context
# Your code here

Hint

Use await get_books_async() inside an async function or view to complete the operation.

Practice

1. What is the main benefit of using Django's async ORM operations?

easy

A. They automatically cache all query results for faster access.

B. They require no use of await keyword in async functions.

C. They convert SQL queries into Python code for easier reading.

D. They allow database queries to run without blocking other tasks.

Solution

1. Step 1: Understand async ORM purpose

   Async ORM lets database queries run without stopping the app, so other tasks continue smoothly.

2. Step 2: Compare options

   Automatic caching is not a feature of async ORM. Converting SQL to Python code is unrelated. Not requiring the await keyword is incorrect. Only allowing database queries to run without blocking other tasks correctly describes the main benefit.

3. Final Answer:

   They allow database queries to run without blocking other tasks. -> Option D

4. Quick Check:

   Async ORM = Non-blocking queries [OK]

Hint: Async ORM means queries don't stop your app [OK]

Common Mistakes:

• Thinking async ORM caches results automatically
• Believing async ORM removes need for await
• Confusing async ORM with query translation

2. Which of the following is the correct syntax to fetch all objects asynchronously using Django's ORM?

easy

A. objects = Model.objects.all()

B. objects = await Model.objects.all()

C. objects = await Model.objects.all().aget()

D. objects = Model.objects.all().await()

Solution

1. Step 1: Recall async ORM syntax

   To fetch all objects asynchronously, use await before the query method returning an awaitable.

2. Step 2: Analyze options

   objects = await Model.objects.all() correctly uses await Model.objects.all(). objects = Model.objects.all().await() misplaces await. objects = await Model.objects.all().aget() wrongly chains .aget() after all(). objects = Model.objects.all() is synchronous.

3. Final Answer:

   objects = await Model.objects.all() -> Option B

4. Quick Check:

   Use await before async ORM calls [OK]

Hint: Use await before async ORM queries [OK]

Common Mistakes:

• Placing await after the query call
• Using synchronous calls without await
• Adding invalid method chains like .aget() after all()

3. Consider this async Django ORM code snippet:

async def get_usernames():
    users = await User.objects.filter(is_active=True).values_list('username', flat=True)
    return list(users)

What will get_usernames() return?

medium

A. A list of usernames of active users

B. A QuerySet of all users including inactive ones

C. A list of all usernames regardless of active status

D. An error because values_list is not async

Solution

1. Step 1: Understand the filter and values_list usage

   The filter limits users to those with is_active=True. The values_list with flat=True returns usernames as a list-like object.

2. Step 2: Recognize async ORM behavior

   Using await fetches the filtered usernames asynchronously. Converting to list returns a list of usernames of active users.

3. Final Answer:

   A list of usernames of active users -> Option A

4. Quick Check:

   Filter + values_list + await = filtered usernames list [OK]

Hint: Filter active users, await values_list, get list [OK]

Common Mistakes:

• Assuming values_list is synchronous and causes error
• Ignoring the filter condition
• Expecting a QuerySet instead of a list

4. Identify the error in this async Django ORM code:

async def get_first_post():
    post = Post.objects.filter(published=True).first()
    return post

medium

A. Using first() synchronously inside async function

B. Missing await before the query causing blocking

C. No error, code is correct

D. Using filter without await is invalid

Solution

1. Step 1: Check async ORM method usage

   first() is a synchronous method and blocks if used inside async function without await.

2. Step 2: Identify correct async method

   Async ORM requires await Post.objects.filter(...).afirst() to fetch first object asynchronously.

3. Final Answer:

   Using first() synchronously inside async function -> Option A

4. Quick Check:

   Use afirst() with await in async functions [OK]

Hint: Use afirst() with await, not first() in async code [OK]

Common Mistakes:

• Forgetting to use await with async ORM calls
• Using synchronous ORM methods inside async functions
• Assuming filter needs await but it returns QuerySet

5. You want to asynchronously update all inactive users to active in Django ORM. Which code snippet correctly performs this update?

hard

A. await User.objects.filter(is_active=False).update(is_active=True)

B. User.objects.filter(is_active=False).update(is_active=True)

C. await User.objects.filter(is_active=False).aupdate(is_active=True)

D. User.objects.filter(is_active=False).aupdate(is_active=True)

Solution

1. Step 1: Identify async update method

   Django async ORM uses aupdate() for asynchronous bulk updates, which must be awaited.

2. Step 2: Analyze options

   await User.objects.filter(is_active=False).aupdate(is_active=True) correctly uses await with aupdate(). User.objects.filter(is_active=False).update(is_active=True) is synchronous. await User.objects.filter(is_active=False).update(is_active=True) uses synchronous update() with await, which is invalid. User.objects.filter(is_active=False).aupdate(is_active=True) misses await.

3. Final Answer:

   await User.objects.filter(is_active=False).aupdate(is_active=True) -> Option C

4. Quick Check:

   Use await with aupdate() for async bulk update [OK]

Hint: Use await with aupdate() for async bulk updates [OK]

Common Mistakes:

• Using synchronous update() with await
• Forgetting to await aupdate()
• Using aupdate() without await