Finding Unvisited URLs with Django ORM

You can use Django's exclude() method with the __in lookup to find URLs that are not in your visited URLs table. Here's how to do it:

Approach 1: Using exclude() with in-memory list

If your model has a URL field and you want to find which URLs from your in-memory list are not in the database:

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from your_app.models import VisitedURL  # Your model that stores visited URLs

# Your in-memory list of URLs
url_list = ['https://example.com', 'https://example.org', 'https://django.com']

# Find URLs from your list that don't exist in the database
unvisited_urls = [url for url in url_list if not VisitedURL.objects.filter(url=url).exists()]

Approach 2: Using values_list() and set operations

For better performance with larger lists:

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from your_app.models import VisitedURL

# Your in-memory list of URLs
url_list = ['https://example.com', 'https://example.org', 'https://django.com']

# Get all visited URLs from the database in a single query
visited_urls = set(VisitedURL.objects.filter(url__in=url_list).values_list('url', flat=True))

# Find unvisited URLs using set difference
unvisited_urls = set(url_list) - visited_urls

The second approach is more efficient as it uses a single database query regardless of the size of your URL list.