{"id":104566,"date":"2024-11-26T21:18:58","date_gmt":"2024-11-26T21:18:58","guid":{"rendered":"https:\/\/www.red-gate.com\/simple-talk\/?p=104566"},"modified":"2024-11-14T21:45:16","modified_gmt":"2024-11-14T21:45:16","slug":"working-with-mongodb-indexes","status":"publish","type":"post","link":"https:\/\/www.red-gate.com\/simple-talk\/databases\/nosql\/mongodb\/working-with-mongodb-indexes\/","title":{"rendered":"Working with MongoDB Indexes"},"content":{"rendered":"

This article is part of Robert Sheldon's continuing series on Mongo DB. To see all of the items in the series, click here<\/a>.<\/strong><\/p>\n\n\n\n\n

Throughout this series, I\u2019ve covered a number of topics about working with MongoDB collections and their data. One topic I have not covered is how to work with indexes. Similar to a relational database system, MongoDB lets you create indexes on your collections to help improve query read performance. You can create an index on one or more fields, even if those fields contain embedded documents, geospatial data, or date and time values.<\/p>\n\n\n\n

In this article, I demonstrate how to create several types of indexes. You\u2019ll also learn how to view existing indexes, drop indexes, and hide them from the query planner. The examples are based on MongoDB Shell commands, rather than the MongoDB Compass interface. By learning the Shell commands, you\u2019ll be able to better understand the principles behind index creation.<\/p>\n\n\n\n

You can access MongoDB Shell through MongoDB Compass or through your system\u2019s command-line interface. Either will serve for this article, where you\u2019ll learn how to create four types of indexes. Although MongoDB also supports other index types, I think you\u2019ll likely use these four basic types initially. From this foundation, you should have no problem creating the other types.<\/p>\n\n\n\n

MongoDB indexes can be extremely useful in supporting your data-driven applications, as long as those indexes are implemented with your workloads in mind. Although they can help speed up read operations, they can also slow down write operations because each data modification requires both the document and index data to be updated.<\/p>\n\n\n\n

Understanding your workloads\u2019 read-to-write ratios will be a key factor in planning an effective indexing strategy. You can also use tools such as the Performance Advisor in MongoDB Atlas to help you determine how best to implement your indexes. Once you\u2019ve decided to add indexes a collection, this article will help you get started.<\/p>\n\n\n\n

Note: For the examples in this article, I used the same MongoDB Atlas environment I used for the previous articles in this series. Refer to the first article for details about setting up these environments. The examples are based on the hr<\/code> database and employees<\/code> collection. You can use a different test database and collection if you like. Just modify the code accordingly.<\/p>\n\n\n\n

Creating indexes in a MongoDB collection<\/h2>\n\n\n\n

You can create an index in MongoDB Shell by using the createIndex<\/code> method, which lets you define different types of indexes based on one or more fields in your collection\u2019s documents. The following syntax shows the basic elements that go into a createIndex<\/code> command:<\/p>\n\n\n\n

db.collection.createIndex( { key }, { options } );<\/pre>\n\n\n\n
The command\u2019s syntax is made up of the following elements:<\/p>\n\n\n
\n