Microsoft DP-420: How to Modify Consistency Level in Azure Cosmos DB Query Requests?

Learn how to adjust the consistency level for read operations in Azure Cosmos DB query requests. Understand the options available and their impact on data consistency.

Question

You have an Azure Cosmos DB for NoSQL account that uses the default consistency level.

How can the consistency level be modified as part of a query request?

A. stronger consistency for write operations
B. weaker consistency for write operations
C. stronger consistency for read operations
D. weaker consistency for read operations

Answer

D. weaker consistency for read operations

Explanation

In Azure Cosmos DB, you can modify the consistency level for read operations as part of a query request. This allows you to temporarily override the default consistency level set on the account for a specific query.

To achieve this, you can use the `ConsistencyLevel` property in the `RequestOptions` class when executing a query. The available options for weaker consistency levels in read operations are:

1. `ConsistencyLevel.Eventual`: This is the weakest consistency level, providing no ordering guarantees. Reads may lag behind writes, and multiple reads of the same data may return different results.

2. `ConsistencyLevel.Session`: This consistency level guarantees that reads within a single client session are consistent. Reads within a session will always see the latest writes from that session, but there’s no guarantee of consistency across sessions.

Here’s an example of how to modify the consistency level for a query request in C#:

var container = client.GetContainer("database", "container");
var query = new QueryDefinition("SELECT * FROM c");

var options = new QueryRequestOptions
{
ConsistencyLevel = ConsistencyLevel.Eventual
};

using (var feed = container.GetItemQueryIterator<dynamic>(query, null, options))
{
while (feed.HasMoreResults)
{
var response = await feed.ReadNextAsync();
foreach (var item in response)
{
Console.WriteLine(item);
}
}
}

In this example, the consistency level is set to `Eventual` for the specific query request, overriding the default consistency level of the Cosmos DB account.

It’s important to note that you can only specify a weaker consistency level than the default level set on the account. For example, if the account’s default consistency level is `Session`, you can only specify `Eventual` or `Session` for the query request. Attempting to set a stronger consistency level will result in an error.

By modifying the consistency level for read operations in query requests, you can fine-tune the balance between data consistency and performance based on your application’s specific requirements.

Microsoft DP-420 certification exam assessment practice question and answer (Q&A) dump including multiple choice questions (MCQ) and objective type questions, with detail explanation and reference available free, helpful to pass the Microsoft DP-420 exam and earn Microsoft DP-420 certification.