M121 Chapter 1: Optional Lab - Expressions with $project - wrong answers

In “Hint” is: “You do not need to count the duplicate entries.”. But when i do group by title, answer is not in answer set. The right answer (right by course) is the one where I don’t protect from duplicate entries. How about this duplicates is?

Hi @Leszek_Mazur,

Please check your discourse inbox and feel free to reach out if you have any questions.


Hi @Sonali_Mamgain ,

I have exactly the same issue and I’m interested in the explanation too

Could you please share it with me?

Best Regards,

Hi @Leszek_Mazur and @Vsevolod_Ryabykh,

You are right!!

The aggregation pipeline is counting duplicate records.

For answering this question, take into consideration these duplicate records. We will get this question updated so that our users do not get confused.

Please feel free to reach out if you have any additional questions.


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