Django prefetch_related Examples|Django select_related and prefetch_related|Django n+1 Query Problem

In this video, I'm gonna be showing you what exactly is prefetch_related in Django. We will demonstrate Django prefetch_related by making use of an example project which has two models and these models are related to each other using a ManytoMany relationship. We will show you what exactly is the use case of Django prefetch_related by querying the Django models and showing the corresponding SQL queries being executed in the background by making use of django debug toolbar. We will then explain the problems with the default accessing method and specifically about the n+1 query problem in Django ORM. Then, we will fix the n+1 problem using Django prefetch_related. We will also talk about the underlying SQL queries being executed if we use prefetch_related. At the end, we will also talk about the difference between prefetch_related and select_related, when to use Django select_related and when to use Django prefetch_related and so on. This video is a part of Django Relationships series.

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[raufp]

Thank you! It is fantastic video. i liked way that demonstrated the use case.After watched videos i was thinking that why didn't see your videos before.

[OrangesDaWin]

Amazing! Thank you for taking the time to explain this!

[harshamachine_learning]

thanks for making video as asked earlier
note you are the only one who made a tutorial video on this

[shampysingh]

Nice . I was avoiding to learn these concepts from djangocon as there videos are very large. But you have helped me to learn what I needed.

[jaydevpatil]

Awesome way to demonstrate the concept 👍🏻

[borin]

that's great vid and easy to understand

[misfarsiddeek]

You are doing great videos brother. Keep going.

[saimaruthi_]

Very helpful & Informative. One small suggestion, please avoid putting background music in your videos :)

[asiannvasion]

Great video, but the background music is very distracting when watching this.

[raghavendrasinghchouhan]

that background music did't bothered much to me but if you control that volume little low it would be great i feel

[deepanshuaggarwal]

in prefetch_related, we are getting list of stores that contain any book as output, not book wise store list. Am i right ?

[vijayl]

if possible make a video for pure graphql, graphene, graphene-django

[shriyahireholi]

what if we use .last() instead of .all() while looping?

[narendrathapa]

anybody can help me which django function we can use for left join or right join.

[jorgeramiroalarconvargas]

you didnt say anythink new but de docs?

[mohdkhalid]

Please increase the font size it is not visible.

[rangabharath]

Please increase font size for this video bro. Not able to see the code ☹️

[oruchkin]

why did you use "store_set" instead of "books" like in documentation? books actually doesnt work, i dont know why
but "store_set" works

[affanarif]

When making an explanation video please remove background music it is very distracting

[saimaruthi_]

If we have three models

class Author(models.Model):
name =
class Book(models.Model):
name=
author = models.ForeignKey(Author, on_delete=models.CASCADE, related_name='books')
class Blog(models.Model):
name=
author = models.ForeignKey(Author, on_delete=models.CASCADE, related_name='blogs)

if we are creating a detailed view of an Author (John), can we use the below querie to fetch all the Books and Blogs he has written?
author = Author.objects.prefetch_related('books_set',
for book in books_set.all():
print(book.name)
for blog in blogs_set.all():
print(blog.name)