Aggregation Concepts

MongoDB aggregation framework provides a way to process and transform data that is stored in our MongoDB collections. It allows you to perform calculations and return the calculated results using various data aggregation tools such as aggregation pipelines, map-reduce functions, or single-purpose aggregation methods.

Here are some of the most important concepts of MongoDB Aggregation:

Example of a simple aggregation pipeline:

  { $match: { status: 'A' } },
  { $group: { _id: '$cust_id', total: { $sum: '$amount' } } },
  { $sort: { total: -1 } },

Each item in the pipeline is a stage. The first stage is a $match stage that filters the documents in the collection. The second stage is a $group stage that groups the documents by the cust_id field and calculates the sum of the amount field. The third stage is a $sort stage that sorts the documents by the total field in descending order.