Django ORM annotation with tree traversal
I'm using the django-mptt library to make categories for my project. The model is pretty simple:
from django.db import models
from mptt.models import MPTTModel, TreeForeignKey
class Category(MPTTModel):
name = models.CharField('Name', max_length=100, unique=True)
color = models.CharField(
'Color',
max_length=100,
blank=True,
null=True
)
parent = TreeForeignKey(
'self',
on_delete=models.CASCADE,
null=True,
blank=True,
related_name='children'
)
class MPTTMeta:
order_insertion_by = ['name']
Category color is optional and should be inherited from parent, if undefined. So just to illustrate:
Main Category 1 (red) -> Subcategory 1
-> Subcategory 2 (blue)
-> Subcategory 3 (yellow) -> Subcategory 4
Subcategory 4 has no color defined and it inherits subcategory 3 color (yellow).
Subcategory 1 inherits color from Main Category 1 (blue), etc.
In my view i have the root category and then build a tree using get_descendants(include_self=True).
How can i annotate color for each category of <TreeQuerySet>?
For one model i have the following method:
@property
def inherited_color(self):
if self.color:
return self.color
return (self
.get_ancestors(ascending=True, include_self=True)
.filter(color__isnull=False)
.values_list('color', flat=True)
.first())
But when this method is called for a list of categories it results in a lot of database queries!
This is an example from django shell:
>>> category
<Category: 3>
>>> category.color is None
True
>>> category.get_family().values_list('name', 'color')
<TreeQuerySet [('1', '#51DCFF'), ('2', None), ('3', None)]>
>>> category.inherited_color
'#51DCFF'
django django-mptt
asked 21 hours ago
v01d
4117
add a comment |
I'm using the django-mptt library to make categories for my project. The model is pretty simple:
from django.db import models
from mptt.models import MPTTModel, TreeForeignKey
class Category(MPTTModel):
name = models.CharField('Name', max_length=100, unique=True)
color = models.CharField(
'Color',
max_length=100,
blank=True,
null=True
)
parent = TreeForeignKey(
'self',
on_delete=models.CASCADE,
null=True,
blank=True,
related_name='children'
)
class MPTTMeta:
order_insertion_by = ['name']
Category color is optional and should be inherited from parent, if undefined. So just to illustrate:
Main Category 1 (red) -> Subcategory 1
-> Subcategory 2 (blue)
-> Subcategory 3 (yellow) -> Subcategory 4
Subcategory 4 has no color defined and it inherits subcategory 3 color (yellow).
Subcategory 1 inherits color from Main Category 1 (blue), etc.
In my view i have the root category and then build a tree using get_descendants(include_self=True).
How can i annotate color for each category of <TreeQuerySet>?
For one model i have the following method:
@property
def inherited_color(self):
if self.color:
return self.color
return (self
.get_ancestors(ascending=True, include_self=True)
.filter(color__isnull=False)
.values_list('color', flat=True)
.first())
But when this method is called for a list of categories it results in a lot of database queries!
This is an example from django shell:
>>> category
<Category: 3>
>>> category.color is None
True
>>> category.get_family().values_list('name', 'color')
<TreeQuerySet [('1', '#51DCFF'), ('2', None), ('3', None)]>
>>> category.inherited_color
'#51DCFF'
django django-mptt
asked 21 hours ago
v01d
4117
add a comment |
I'm using the django-mptt library to make categories for my project. The model is pretty simple:
from django.db import models
from mptt.models import MPTTModel, TreeForeignKey
class Category(MPTTModel):
name = models.CharField('Name', max_length=100, unique=True)
color = models.CharField(
'Color',
max_length=100,
blank=True,
null=True
)
parent = TreeForeignKey(
'self',
on_delete=models.CASCADE,
null=True,
blank=True,
related_name='children'
)
class MPTTMeta:
order_insertion_by = ['name']
Category color is optional and should be inherited from parent, if undefined. So just to illustrate:
Main Category 1 (red) -> Subcategory 1
-> Subcategory 2 (blue)
-> Subcategory 3 (yellow) -> Subcategory 4
Subcategory 4 has no color defined and it inherits subcategory 3 color (yellow).
Subcategory 1 inherits color from Main Category 1 (blue), etc.
In my view i have the root category and then build a tree using get_descendants(include_self=True).
How can i annotate color for each category of <TreeQuerySet>?
For one model i have the following method:
@property
def inherited_color(self):
if self.color:
return self.color
return (self
.get_ancestors(ascending=True, include_self=True)
.filter(color__isnull=False)
.values_list('color', flat=True)
.first())
But when this method is called for a list of categories it results in a lot of database queries!
This is an example from django shell:
>>> category
<Category: 3>
>>> category.color is None
True
>>> category.get_family().values_list('name', 'color')
<TreeQuerySet [('1', '#51DCFF'), ('2', None), ('3', None)]>
>>> category.inherited_color
'#51DCFF'
django django-mptt
asked 21 hours ago
v01d
4117
I'm using the django-mptt library to make categories for my project. The model is pretty simple:
from django.db import models
from mptt.models import MPTTModel, TreeForeignKey
class Category(MPTTModel):
name = models.CharField('Name', max_length=100, unique=True)
color = models.CharField(
'Color',
max_length=100,
blank=True,
null=True
)
parent = TreeForeignKey(
'self',
on_delete=models.CASCADE,
null=True,
blank=True,
related_name='children'
)
class MPTTMeta:
order_insertion_by = ['name']
Category color is optional and should be inherited from parent, if undefined. So just to illustrate:
Main Category 1 (red) -> Subcategory 1
-> Subcategory 2 (blue)
-> Subcategory 3 (yellow) -> Subcategory 4
Subcategory 4 has no color defined and it inherits subcategory 3 color (yellow).
Subcategory 1 inherits color from Main Category 1 (blue), etc.
In my view i have the root category and then build a tree using get_descendants(include_self=True).
How can i annotate color for each category of <TreeQuerySet>?
For one model i have the following method:
@property
def inherited_color(self):
if self.color:
return self.color
return (self
.get_ancestors(ascending=True, include_self=True)
.filter(color__isnull=False)
.values_list('color', flat=True)
.first())
But when this method is called for a list of categories it results in a lot of database queries!
This is an example from django shell:
>>> category
<Category: 3>
>>> category.color is None
True
>>> category.get_family().values_list('name', 'color')
<TreeQuerySet [('1', '#51DCFF'), ('2', None), ('3', None)]>
>>> category.inherited_color
'#51DCFF'
django django-mptt
django django-mptt
asked 21 hours ago
v01d
4117
asked 21 hours ago
v01d
4117
edited 17 hours ago
asked 21 hours ago
v01d
4117
asked 21 hours ago
v01d
4117
asked 21 hours ago
v01d
4117
4117
add a comment |
add a comment |
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