Django Bulk Update QuerySet objects


Author: Meet Rajesh Gor

#django #python

Let's say, I have a lots of objects which I want to update with a particular field or fields. We can use the bulk_update method with the model name.

# blog/

from django.db import models

    ("PUBLISHED", "Published"),
    ("DRAFT", "Draft"),

class Article(models.Model):
    title = models.CharField(max_length=128)
    description = models.CharField(max_length=512)
    content = models.TextField()
    status = models.CharField(max_length=16, choices=ARTICLE_STATUS, default="DRAFT")

    def __str__(self):
        return self.title

Let's say we have a simple model Article with a few typical attributes like title, description, content, and status. We have the status as a choice field from two options as Draft and Published. It could be a boolean field, but that looks too gross for a article status.

from blog.models import Article

articles = Article.objects.filter(status="draft")

for i in range(len(articles)):
    articles[i].status = "published"

Article.objects.bulk_update(articles, ["status",])

In the above code, the Articles model is filtered by the status of draft. We iterate over the QuerySet which will contain the objects of the articles, by setting the object's properties to the value we want to set. We are jsut setting the value of the property of the object for each object.

This just makes a changes to the QuerySet, by using the bulk_update method, the two parameters required are the QuerySet and the list of fields which are to be updated. The function returns the number of objects/records updated.

>>> from blog.models import Article
>>> articles = Article.objects.filter(status="DRAFT")
>>> articles
<QuerySet [<Article: test 1>, <Article: test 3>]>

>>> for i in range(len(articles)):
...     articles[i].status = "PUBLISHED"
>>> articles
<QuerySet [<Article: test 1>, <Article: test 3>]>

>>> Article.objects.bulk_update(articles, ['status',])

>>> Article.obejcts.get(title="test 1").status

>>> Article.objects.filter(status="DRAFT")
<QuerySet []>

As, we can see here there were two obejcts test 1 and test 2 objects with the status as Draft. By iterating over the queryset and assigning the status of the object to published, the query set was changed and modified locally. By using the bulk_update method, we parsed the queryset and the list of attributes to be updated into the function. This gives us the number of objects which were updated, in this case 2. We then look into the article actual record in the database and it has indeed updated to the value we set in this operation.

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