Book Image

Mastering MongoDB 3.x

By : Alex Giamas
Book Image

Mastering MongoDB 3.x

By: Alex Giamas

Overview of this book

MongoDB has grown to become the de facto NoSQL database with millions of users—from small startups to Fortune 500 companies. Addressing the limitations of SQL schema-based databases, MongoDB pioneered a shift of focus for DevOps and offered sharding and replication maintainable by DevOps teams. The book is based on MongoDB 3.x and covers topics ranging from database querying using the shell, built in drivers, and popular ODM mappers to more advanced topics such as sharding, high availability, and integration with big data sources. You will get an overview of MongoDB and how to play to its strengths, with relevant use cases. After that, you will learn how to query MongoDB effectively and make use of indexes as much as possible. The next part deals with the administration of MongoDB installations on-premise or in the cloud. We deal with database internals in the next section, explaining storage systems and how they can affect performance. The last section of this book deals with replication and MongoDB scaling, along with integration with heterogeneous data sources. By the end this book, you will be equipped with all the required industry skills and knowledge to become a certified MongoDB developer and administrator.
Table of Contents (13 chapters)

Aggregation operators

In this section we will explain how to use aggregation operators. Aggregation operators are divided into two parts. Within each stage, we use expression operators to compare and process values. Between different stages, we use aggregation stage operators to define the data that will get passed on from one stage to the next as its as the format.

Aggregation stage operators

An aggregation pipeline is composed of different stages. These stages are declared in an array and executed sequentially, the output of every stage being the input of the next one.

The $out stage has to be the final stage in an aggregation pipeline, outputting data to an output collection by replacing or adding to the existing documents...