Removing objects from a queryset by ID optimal implementation

Question

I have a queryset of 1000000 objects MyModel.
All objects in queryset have an ID.

I pass a list of ids to remove, for example:

ids = ['1', '23', '117', ...] # len = 100000

Then, i need to delete objects in queryset with ids.

List of ids can contains non-existent ids.

What is the best way to do it?

My variant:

for id in ids:
    obj = MyModel.objects.filter(pk=id)
    if obj:
        obj.delete()

I’m not sure about it, because it will make a 100000 queries to the database, maybe it makes sense to convert the queryset to a list, then filter it by id?

On the other hand, if there are a million objects in the database, and only one needs to be deleted, this will create an inverse relationship.

Asked By: Anonymous Wizard

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Source

Answer 1

The current approach will query the database 1000000 times, you can use __in
lookup and do bulk deletion by applying delete() just after filter():

MyModel.objects.filter(pk__in=ids).delete()

Now the database would be affected only one time.

Edit:

To filter all the valid IDs in optimal way do intersection in the following way:

all_existing_ids = set(MyModel.objects.values_list('pk', flat=True))
all_valid_ids = set(ids) & existing_ids

Answered By: Sunderam Dubey

Removing objects from a queryset by ID optimal implementation

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