Mastering Cosmos DB through Basic and Advanced Concepts with C#/

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Overview of Indexing Policies

Overview of Indexing Policies

Learn how to create indexing policies on a Cosmos DB container to improve query performance and reduce costs.

We'll cover the following...

Indexing in Cosmos DB

By default, Cosmos DB indexes every property in a document. This approach improves efficiency when we use the WHERE or ORDER BY clauses on a single property.

Property path mapping

It’s out of the scope of this lesson to teach how Cosmos DB creates indexes, but it’s interesting to have a small overview.

When requesting the creation of an item, the database does the following:

  • Projects the item as a JSON document.

  • Converts the item into a tree and updates indexes.

This process helps the engine extract the path of a value by traversing the tree and concatenating each node label.

For example, take a look at the following document:

{
  "title": "Game A",
  "price": 19.99,
  "developer": {
    "name": "Publisher A"
    "country": "US"
  }  
}
Example of a "game" document

It is converted into the following tree:

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Tree representation of a game document
Tree representation of a game document

This structure makes it easy to extract the following paths during queries:

  • /title: Game A

  • /price: 19.99

  • /developer/name: Publisher A

  • /developer/country: US

Type of indexes

There are three types of indexes we can define:

  • Range index

  • Spatial index

  • Composite ...