Overview
Aggregation framework
Aggregation framework in MongoDB is a powerful feature that allows you to build complex queries that you normally cannot build with the common operators and functions. The framework achieves this by putting your documents into a multi-stage pipeline that transforms the documents in the desired result.
Pipeline
The pipeline consists of a series of stages where each stage receives the output of the previous stage. The section contains samples for the following stages:
Stage | Description |
Project | Adds new fields or removes existing ones |
Match | Filters the documents |
Group | Groups documents by an identifier expression providing accumulator results |
Unwind | Deconstructs an array field |
Pagination (limit, skip) | Skips the first n documents and limits the total results |
Bucket | Produces a distribution among documents based on a specified expression and specified boundaries |
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