django - How to add an annotation on distinct items?

Question

I've got a query...

packages = Package.objects.annotate(bid_count=Count('items__bids'))

Which is supposed to give me a list of packages with the number of bids each. It works great if there's only one item in the package, but if there's more it double counts.

Each package consists of 1 or more items. Each bid is placed on 1 or more items within a package. I want to retrieve the number of bids placed on the items within that package.

If there is 1 bid placed on 2 items within a package, presently this will count as 2, I want it to return 1.

I tried Count('items__bids__distinct') but that didn't work. How can I do this?

question from:https://stackoverflow.com/questions/4048014/how-to-add-an-annotation-on-distinct-items

Answer 1

I had the same problem and I found the resolution:

packages = Package.objects.annotate(bid_count=Count('items__bids', distinct = True))