Aggregation

Aggregations operations process data records and return computed results. Aggregation operations group values from multiple documents together, and can perform a variety of operations on the grouped data to return a single result. MongoDB provides three ways to perform aggregation: the aggregation pipeline, the map-reduce function, and single purpose aggregation methods and commands.

You can download this section in PDF form as MongoDB Aggregation and Data Processing.

Aggregation Introduction

A high-level introduction to aggregation.

Aggregation Concepts

Introduces the use and operation of the data aggregation modalities available in MongoDB.

Aggregation Pipeline

The aggregation pipeline is a framework for performing aggregation tasks, modeled on the concept of data processing pipelines. Using this framework, MongoDB passes the documents of a single collection through a pipeline. The pipeline transforms the documents into aggregated results, and is accessed through the aggregate database command.

Map-Reduce

Map-reduce is a generic multi-phase data aggregation modality for processing quantities of data. MongoDB provides map-reduce with the mapReduce database command.

Single Purpose Aggregation Operations

MongoDB provides a collection of specific data aggregation operations to support a number of common data aggregation functions. These operations include returning counts of documents, distinct values of a field, and simple grouping operations.

Aggregation Mechanics

Details internal optimization operations, limits, support for sharded collections, and concurrency concerns.

Aggregation Examples

Examples and tutorials for data aggregation operations in MongoDB.

Aggregation Reference

References for all aggregation operations material for all data aggregation methods in MongoDB.

• Aggregation Introduction
• Aggregation Concepts
  • Aggregation Pipeline
  • Map-Reduce
  • Single Purpose Aggregation Operations
  • Aggregation Mechanics
    • Aggregation Pipeline Optimization
    • Aggregation Pipeline Limits
    • Aggregation Pipeline and Sharded Collections
    • Map-Reduce and Sharded Collections
    • Map Reduce Concurrency
• Aggregation Examples
  • Aggregation with the Zip Code Data Set
  • Aggregation with User Preference Data
  • Map-Reduce Examples
  • Perform Incremental Map-Reduce
  • Troubleshoot the Map Function
  • Troubleshoot the Reduce Function
• Aggregation Reference
  • Aggregation Pipeline Quick Reference
  • Aggregation Commands Comparison
  • SQL to Aggregation Mapping Chart
  • Aggregation Commands
  • Variables in Aggregation Expressions

Additional Resources

• MongoDB Analytics: Learn Aggregation by Example: Exploratory Analytics and Visualization Using Flight Data
• MongoDB for Time Series Data: Analyzing Time Series Data Using the Aggregation Framework and Hadoop
• The Aggregation Framework
• Webinar: Exploring the Aggregation Framework
• Quick Reference Cards

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