Django: Fastest way to query & group a queryset by a ManyToManyField

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I have two models - a Product & Category. In my template, I want to display the products by the Category.

class Category(models.Model):
 name = models.CharField()

class Product(models.Model):
 name = models.CharField()
 categories = models.ManyToManyField(Category)

Slow solution

The most basic way to do this, query the Categories and in the template loop over the products.

% for category in object_list %
 % for product in category.products.all %
 < html to display the product >
 % endfor %
% endfor %

This results in hundreds of queries and is very slow.

Question

What would be better way to handle this query so that there are as few queries as possible with a faster load time?

edited Nov 15 '18 at 16:03

asked Nov 15 '18 at 15:57

Emile

1,72863064

2

You should use prefetch_related('product') on your category query. Then if you want to group stuff by some field you should be able to use the template 'regroup' tag, though I have never used it for many to many before. See docs.djangoproject.com/en/2.1/ref/templates/builtins/#regroup for an example.

– DisneylandSC
Nov 15 '18 at 16:04

add a comment |

I have two models - a Product & Category. In my template, I want to display the products by the Category.

class Category(models.Model):
 name = models.CharField()

class Product(models.Model):
 name = models.CharField()
 categories = models.ManyToManyField(Category)

Slow solution

The most basic way to do this, query the Categories and in the template loop over the products.

% for category in object_list %
 % for product in category.products.all %
 < html to display the product >
 % endfor %
% endfor %

This results in hundreds of queries and is very slow.

Question

What would be better way to handle this query so that there are as few queries as possible with a faster load time?

edited Nov 15 '18 at 16:03

asked Nov 15 '18 at 15:57

Emile

1,72863064

2

You should use prefetch_related('product') on your category query. Then if you want to group stuff by some field you should be able to use the template 'regroup' tag, though I have never used it for many to many before. See docs.djangoproject.com/en/2.1/ref/templates/builtins/#regroup for an example.

– DisneylandSC
Nov 15 '18 at 16:04

add a comment |

I have two models - a Product & Category. In my template, I want to display the products by the Category.

class Category(models.Model):
 name = models.CharField()

class Product(models.Model):
 name = models.CharField()
 categories = models.ManyToManyField(Category)

Slow solution

The most basic way to do this, query the Categories and in the template loop over the products.

% for category in object_list %
 % for product in category.products.all %
 < html to display the product >
 % endfor %
% endfor %

This results in hundreds of queries and is very slow.

Question

What would be better way to handle this query so that there are as few queries as possible with a faster load time?

edited Nov 15 '18 at 16:03

asked Nov 15 '18 at 15:57

Emile

1,72863064

I have two models - a Product & Category. In my template, I want to display the products by the Category.

class Category(models.Model):
 name = models.CharField()

class Product(models.Model):
 name = models.CharField()
 categories = models.ManyToManyField(Category)

Slow solution

The most basic way to do this, query the Categories and in the template loop over the products.

% for category in object_list %
 % for product in category.products.all %
 < html to display the product >
 % endfor %
% endfor %

This results in hundreds of queries and is very slow.

Question

What would be better way to handle this query so that there are as few queries as possible with a faster load time?

django django-models

edited Nov 15 '18 at 16:03

asked Nov 15 '18 at 15:57

Emile

1,72863064

edited Nov 15 '18 at 16:03

asked Nov 15 '18 at 15:57

Emile

1,72863064

edited Nov 15 '18 at 16:03

asked Nov 15 '18 at 15:57

Emile

1,72863064

asked Nov 15 '18 at 15:57

Emile

1,72863064

asked Nov 15 '18 at 15:57

Emile

1,72863064

2

You should use prefetch_related('product') on your category query. Then if you want to group stuff by some field you should be able to use the template 'regroup' tag, though I have never used it for many to many before. See docs.djangoproject.com/en/2.1/ref/templates/builtins/#regroup for an example.

– DisneylandSC
Nov 15 '18 at 16:04

add a comment |

2

You should use prefetch_related('product') on your category query. Then if you want to group stuff by some field you should be able to use the template 'regroup' tag, though I have never used it for many to many before. See docs.djangoproject.com/en/2.1/ref/templates/builtins/#regroup for an example.

– DisneylandSC
Nov 15 '18 at 16:04

You should use prefetch_related('product') on your category query. Then if you want to group stuff by some field you should be able to use the template 'regroup' tag, though I have never used it for many to many before. See docs.djangoproject.com/en/2.1/ref/templates/builtins/#regroup for an example.

– DisneylandSC
Nov 15 '18 at 16:04

add a comment |

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