Aggregation framework
In the following pages, we will try to provide a brief introduction to the MongoDB aggregation framework, what it is, what benefits it offers, and why it is regarded as one of the strongest selling points of the MongoDB ecosystem.
Centered around the concept of a pipeline (something that you might be familiar with if you have done some analytics or if you have ever connected a few commands in Linux), the aggregation framework is, at its simplest, an alternative way to retrieve sets of documents from a collection; it is similar to the find method that we already used extensively but with the additional benefit of the possibility of data processing in different stages or steps.
With the aggregation pipeline, we basically pull documents from a MongoDB collection and feed them sequentially to various stages of the pipeline where each stage output is fed to the next stage’s input until the final set of documents is returned. Each stage performs some data...
