Maintaining index policies is one of the most pivotal operations for Azure Cosmos DB. This ensures optimal performance for particular workloads, as the index policy directly that affects how your queries are served. In the case of a Cosmos DB instance, indexing policies define how items on each single collection are indexed.
As you may know, Azure Cosmos DB is a globally distributed document-oriented database service that offers NoSQL data storage. One of its critical features is the power it gives developers to manage the indexing strategy of the database.
Let’s discuss how these indexing policies can be maintained in a production environment via Azure Resource Manager (ARM) templates.
Understanding Indexing Policies in Azure Cosmos DB
Indexing in Azure Cosmos DB performs automatic indexing by default unless explicitly turned off. The Azure Cosmos DB indexing policy determines the paths in your documents that are indexed, the kind of index (range or spatial) and the indexing mode (consistent or lazy).
An indexing policy consists of the following four parts:
- Indexing Mode: This can be either ‘Consistent’ or ‘Lazy’. Consistent indexing is updated synchronously as data is written to the database. Lazy is an asynchronous operation and can lag behind writes.
- Automatic: A boolean parameter, when set to ‘True’, all document paths will be indexed by default, and when set to ‘False’ only paths listed in the ‘IncludedPaths’ are indexed.
- Included Paths: They indicate which paths to be excluded in the default indexing and must be manually specified.
- Excluded Paths: These are paths that will not be indexed even though the ‘Automatic’ setting is ‘True’.
Working with ARM Templates
Azure Resource Manager (ARM) templates are JavaScript Object Notation (JSON) files that define the infrastructure and configuration for your project. These architectures allow you to use declarative syntax to deploy and manage resources associated with your project.
ARM Templates are a comprehensive way to create and maintain resources for Azure Cosmos DB. ARM templates are critical in production environments as they allow infrastructure as code and enable automation and collaboration in deployment.
ARM template components include:
- Resources: These are the resources to deploy or update.
- Parameters: These values are used to customize resource deployment.
- Variables: These values are used as constants in the template.
- Functions: These are user-defined functions that simplify complex expressions.
Maintaining Indexing Policies Using ARM Templates
To integrate ARM templates with Azure Cosmos DB for maintaining Index Policies, we must include the configuration for indexing policies as part of our Cosmos DB ARM Template.
Below is an example of how to implement this in your ARM templates:
“properties”: {
“indexingPolicy”: {
“indexingMode”: “consistent”,
“automatic”: true,
“includedPaths”: [
{
“path”: “/*”
}
],
“excludedPaths”: [
{
“path”: “/\”_etag\”/?”
}
]
}
}
In the above example, we’ve specified an indexing policy that applies consistent indexing (`indexingMode: consistent`) and also automatically indexes all paths (`automatic: true`).
The `”includedPaths”` section specifies all paths `”path”: “/*”`, that should be indexed. And the `”excludedPaths”` section specifies the paths `”path”: “/\”_etag\”/?”` that should not be indexed.
By deploying the ARM template, this defined indexing policy will be applied during the creation or update of a Cosmos DB instance.
To conclude, ARM templates are a great way for maintaining indexing policies in Azure Cosmos DB. Indexing Policies are critical for achieving high query performance in Cosmos DB and ARM templates allow us to persist and version these settings in a production environment. Notably, indexing doesn’t just happen automatically, it needs careful planning and should always satisfy the application latency needs with minimum usage of storage resources.
Practice Test
True or False: Azure Resource Manager (ARM) templates can be used to automate deployment and configuration of indexing policies in production.
- True
- False
Answer: True
Explanation: ARM templates support indexing policies, which can be used for automating deployment and configuring indexing policies in a production environment.
Multiple select: Which of the following can be configured using indexing policies in Azure Cosmos DB?
- a) Precision
- b) Included Paths
- c) Excluded Paths
- d) Storage Account
Answer: a), b), c)
Explanation: An indexing policy defines precision, included paths, and excluded paths. A storage account is not configured using indexing policies.
True or False: ARM templates cannot be used to manage multiple resources and resource groups in Azure.
- True
- False
Answer: False
Explanation: ARM templates are the deployment service for Azure, allowing you to create and manage resources more effectively.
Single select: ARM templates are written in which language?
- a) JSON
- b) Python
- c) JavaScript
- d) Java
Answer: a) JSON
Explanation: ARM templates are written in JSON (JavaScript Object Notation), a language-independent open standard format.
Multiple select: What do indexing policies in Azure Cosmos DB control?
- a) What parts of an item’s content to index
- b) The precision of the index
- c) The Azure region
- d) The cost of index storage
Answer: a), b), d)
Explanation: Indexing policies determine what parts of an item’s content to index, the precision of the index and indirectly influence the cost of index storage. The Azure region is not controlled by indexing policies.
True or False: It is possible to modify the indexing policy of an existing Azure Cosmos container by using ARM templates.
- True
- False
Answer: True
Explanation: We can indeed modify the indexing policy of an existing Azure Cosmos container by using the ARM templates.
Multiple select: Which of the following operations can be performed with ARM templates?
- a) Deployment of resources
- b) You can run complex queries
- c) Management of access policies
- d) Organizing resources
Answer: a), c), d)
Explanation: ARM templates can be used to automate deployment, manage access policies, and organize resources effectively. Running complex queries is not a feature of ARM templates.
Single select: What is the main purpose of ARM templates?
- a) To automate deployment
- b) To manage storage
- c) To create virtual machines
- d) All of the above
Answer: a) To automate deployment
Explanation: The main purpose of ARM templates is to automate deployment and configuration of resources in Azure.
True or False: Indexing policies in Azure Cosmos DB do not affect query performance.
- True
- False
Answer: False
Explanation: Indexing policies in Azure Cosmos DB do actually affect query performance as well as the cost of read and write operations.
Single select: Which of the following concepts is NOT associated with Azure Cosmos DB’s indexing policy?
- a) Indexing mode
- b) Indexing path
- c) Consistency level
- d) Indexing precision
Answer: c) Consistency level
Explanation: Consistency level is not a part of Azure Cosmos DB’s indexing policy, it is a separate concept related to read operations in Azure Cosmos DB.
Interview Questions
What is an ARM template in Azure?
An ARM (Azure Resource Manager) template is a JSON file used in Azure to automate deployments. It defines the resources needed for an application so that Azure can understand how to provision and configure these resources efficiently.
How is Cosmos DB indexing policy maintained in production with ARM templates?
Cosmos DB indexing policy is maintained in production using ARM templates by defining the indexing policy in the template. This has all the indexes that should be included or excluded, indexing mode and automatic indexing. This template can be used to automate the deployment and updates of the Cosmos DB instances in production.
Can you modify the indexing policy of an Azure Cosmos DB container using ARM templates without recreating the container?
No, you cannot modify the indexing policy of an Azure Cosmos DB container using ARM templates without recreating the container. Any change in an indexing policy necessitates the recreation of a container in Azure Cosmos DB.
What is an indexing policy in the context of Cosmos DB?
An indexing policy in Cosmos DB defines how items in the database are indexed. It includes settings for automatic indexing, index types, index path, and indexing mode.
How does Cosmos DB handle indexing by default?
By default, Cosmos DB automatically indexes all properties in all items in a container without having to be explicitly specified by an indexing policy.
What is an index transformation in Cosmos DB?
Index transformation is a process in Cosmos DB that rebuilds the indexes based upon changes in the indexing policy. This process is required when making changes to the indexing policy, ensuring that the current data complies with the new policy.
What indexing modes are available in Cosmos DB?
Cosmos DB has two indexing modes: Consistent and Lazy. Consistent indexing is updated synchronously as data is written to the database while Lazy indexing is updated asynchronously.
What is the role of the “excludedPaths” property in Azure Cosmos DB ARM templates?
The “excludedPaths” property in Azure Cosmos DB ARM templates allows specific areas in the document path hierarchy to be excluded from indexing, improving the performance of write operations and reducing storage of the indexing data.
Is using ARM templates to maintain indexing policies in a Cosmos DB environment mandatory?
No, it’s not mandatory but it is recommended for deploying repeatable and consistent Cosmos DB environments. Especially in production environments, it ensures indexing settings remain consistent across deployments.
Where can I find examples of Cosmos DB ARM templates?
Examples of Cosmos DB ARM templates can be found in the official Azure Quickstart Templates repository on GitHub.
How does the “includedPaths” property in an ARM template function?
The “includedPaths” property specifies the paths within the document that should be included in the index.
What is the standard way to update a Cosmos DB index using ARM Templates?
The standard way to update a Cosmos DB index using ARM Templates is to modify the index policy in the ARM template and redeploy it, causing the entire Azure Cosmos DB container to be dropped and recreated.
What is the cost of indexing in Cosmos DB?
The cost of indexing in Cosmos DB is based on the storage size of the index and the provisioned throughput required to maintain the index. Higher indexing can lead to increased cost.
Using ARM Templates, how can you set the indexing mode in Cosmos DB?
In ARM Templates, you can set the indexing mode in Cosmos DB by including an ‘indexingPolicy’ object in your template, along with an ‘indexingMode’ property set to either ‘Consistent’ or ‘Lazy’.
Can I use indexing policies in Azure Cosmos DB to optimize query performance?
Yes, adjusting the indexing policies in Azure Cosmos DB provides the flexibility to optimize read-heavy or write-heavy scenarios, which can improve overall query performance.
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