What is the Aggregation Framework in MongoDB?

1.	What is the Aggregation Framework in MongoDB?
Answer» The aggregation framework is a SET of ANALYTICS tools within MongoDB that allow you to do analytics on documents in one or more collections. The aggregation framework is based on the concept of a pipeline. With an aggregation pipeline, we take input from a MongoDB collection and pass the documents from that collection through one or more stages, each of which performs a different operation on its INPUTS (See FIGURE below). Each STAGE takes as input whatever the stage before it produced as output. The inputs and outputs for all stages are documents—a stream of documents.

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