MongoDB Aggregation Framework Masterclass

MongoDB's Aggregation Framework is a powerful tool for running multi-stage analytical queries directly on your database. Let's explore the core pipeline stages.

1. What is an Aggregation Pipeline?

An aggregation pipeline consists of one or more stages that process documents sequentially. Each stage performs an operation (filtering, grouping, reshaping) and passes the result to the next stage.

2. Key Pipeline Stages

• $match: Filters documents based on conditions (similar to query filters).
• $group: Groups documents by a specified key and performs accumulative operations (like sums, averages).
• $project: Reshapes documents by adding, renaming, or removing fields.
• $lookup: Performs left-outer joins with other collections.

db.orders.aggregate([
  { $match: { status: "completed" } },
  { $group: { _id: "$customerId", totalSpent: { $sum: "$amount" } } }
]);

Final Thoughts

Minimize the amount of data processed by placing $match stages at the very beginning of your pipeline to leverage database indexes.

Happy Coding!