CODEWITHSUNDEEP
pythondjango
Don
Don

Reputation: 125

How to resolve inconsistent annotation in Django?

I have the following 2 lines of 

CategoryContext = Somemodel.objects.values('title__categories__category').distinct()
CategoryContextSum = CategoryContext.annotate(Total_Revenue=Sum('revenue')).order_by('-Total_Revenue')
CategoryContextAvg = CategoryContext.annotate(Average_Revenue=Avg('revenue')).order_by('-Average_Revenue')

The avg query yields a querylist of objects where the category comes first, followed by the revenue. So basically:

<QuerySet [{'title__categories__category':'Category', 'Average_Revenue':Decimal('100'),}, {'title__categories__category':'Category2':'Average_Revenue':Decimal('120'), }]>

The sum query on the other hand yields the revenue followed by the category, so basically:

<QuerySet [{'Total_Revenue':Decimal('100'), 'title__categories__category':'Category'}, {'Total_Revenue':Decimal('120'), 'title__categories__category':'Category2'}]>

Now I have tried flipping the queries around and changing the variable names so far, but I cannot seem to figure out why in the heck these 2 statements are behaving so differently. Does anybody know what could influence annotation behavior in Django?

Edit: In case you are wondering why I need to understand this: I am passing the queryset to a method that turns it into data for generating a barchart and the first object in the dataset must be the identifier of the value. I could make it so that it inverts the whole process by checking whether this indeed is the case and ivnerting otherwise, but it seems to me that this shouldnt be necessary

Upvotes: 1

Views: 60

Answers (1)

Moses Koledoye
Moses Koledoye

Reputation: 78546

This has little or nothing to do with annotate. Dictionaries in Python have no conventional sense of ordering (at least not until Python 3.6), and keys can be ordered differently across different queryset results.

And this constitutes little or not problem since you'll be access required values by key and not serially (as with sequences):

for obj_dct in your_qs:
    print(obj_dct[some_key])

If your plot function takes dicts, no need to worry about ordering.

Upvotes: 3

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