To add a new primary key in Django Cassandra so that a specific column can be filtered by a list of values, you need to make changes to the model definition and the corresponding Cassandra table. Here’s an example:

1. Modify the model definition: In your Django model, you can add a new field to the primary key by creating a new model class that inherits from the original model and adding the desired field to the primary key.

from django_cassandra_engine.models import DjangoCassandraModel

class Task(DjangoCassandraModel):
    task_id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    task_name = models.TextField()
    task_description = models.TextField()

class TaskWithTaskName(Task):
    class Meta:
        primary_key = ('task_name', 'task_id')

1. Update the Cassandra table: To make this change in the underlying Cassandra table, you will need to drop the old table and create a new one with the updated primary key. You can use a Django management command or perform the necessary CQL statements directly in the Cassandra shell to accomplish this.

Here’s an example management command:

from django.core.management.base import BaseCommand
from django.db import connections

class Command(BaseCommand):
    help = 'Add new primary key to the TaskWithTaskName model'

    def handle(self, *args, **options):
        connection = connections['cassandra']
        with connection.cursor() as cursor:
            cursor.execute("DROP TABLE task;")
            cursor.execute("CREATE TABLE task (task_name text, task_id uuid, task_description text, PRIMARY KEY (task_name, task_id));")

After running this command, you should be able to query the TaskWithTaskName model using the task_name field in filters.

tasks = TaskWithTaskName.objects.filter(task_name__in=['Task A', 'Task B'])

Keep in mind that adding a new primary key can have performance implications for your Cassandra cluster, as it will affect the distribution of data across nodes and the efficiency of queries. You should consider the trade-offs carefully before making this change to your data model.