Problem Statement
Explain what the MongoDB Aggregation Framework is and how it differs from regular find queries.
Explanation
The Aggregation Framework is a powerful data processing pipeline in MongoDB that allows you to perform complex transformations, computations, and analytics on documents. Unlike find queries which simply retrieve documents, aggregation can transform, group, calculate, and reshape data.
Aggregation works by passing documents through a multi-stage pipeline where each stage performs a specific operation like filtering, grouping, sorting, or reshaping. Documents flow from one stage to the next, with each stage transforming the data.
The key difference from find is that aggregation can perform calculations like sums, averages, and counts, group documents by fields, join collections using dollar lookup, and create completely new document structures. Find queries are limited to filtering and projecting existing fields, while aggregation enables complex data analysis directly in the database.
Common aggregation stages include dollar match for filtering, dollar group for aggregation, dollar project for reshaping, dollar sort for ordering, dollar limit and dollar skip for pagination, and dollar lookup for joins.
Code Solution
SolutionRead Only
// Find query - simple retrieval
db.orders.find({ status: "completed" }, { customer: 1, total: 1 })
// Aggregation - complex analysis
db.orders.aggregate([
{ $match: { status: "completed" } },
{ $group: { _id: "$customer", totalSpent: { $sum: "$total" } } },
{ $sort: { totalSpent: -1 } },
{ $limit: 10 }
])