Summary
We started this chapter by learning how to update documents using aggregation pipeline support. Pipeline support, which was introduced in MongoDB version 4.2, helps us to perform some complex updates. Using pipeline support, we can write multi-stage update expressions, where the output of a stage is provided as input to the next stage. It also allows us to use field references and aggregation operators. We also learned how to manipulate elements in array fields, how to add, remove, and update elements in an array, how to sort an array, and how to add only unique elements to an array.
In the next chapter, we will learn about MongoDB aggregation framework and pipeline in detail.