Queries

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Category: Server-Side Programming

Summary: Queries

Overview

using Microsoft.Azure.Cosmos;
using System;
using System.Threading.Tasks;

public async Task RunParameterizedQueryAsync(Container container, string customerId, string status)
{
    // 1. Define the SQL query text using parameter placeholders (@customerId, @status)
    string sqlText = "SELECT * FROM c WHERE c.customerId = @customerId AND c.status = @status";

    // 2. Create the QueryDefinition and bind the dynamic values safely
    QueryDefinition queryDefinition = new QueryDefinition(sqlText)
        .WithParameter("@customerId", customerId)
        .WithParameter("@status", status);

    // 3. Execute the query using GetItemQueryIterator
    using FeedIterator feedIterator = container.GetItemQueryIterator(queryDefinition);

    while (feedIterator.HasMoreResults)
    {
        FeedResponse response = await feedIterator.ReadNextAsync();
        foreach (Order order in response)
        {
            Console.WriteLine($"Found Order ID: {order.Id}");
        }
    }
}

  

More Info & Links

• Microsoft Learn: Handling rate limiting / request rate too large

DP-420 Style Practice Questions

Q1. What does a 429 error from Azure Cosmos DB typically indicate?

• A. The request was throttled because provisioned throughput (RU/s) was exceeded
• B. The requested item does not exist
• C. An authentication failure occurred
• D. A conflict occurred during multi-region writes

Q2. Which of these could help reduce the frequency of 429 errors?

• A. Improving partition key distribution to avoid hot partitions, or increasing provisioned RU/s
• B. Disabling the SDK's automatic retry policy
• C. Switching to gateway mode exclusively
• D. Reducing the number of properties indexed

Answer Key

Answers are listed at the very end so you can attempt the questions first.

• Q1 (429 Throttling Error): A. The request was throttled because provisioned throughput (RU/s) was exceeded — A 429 status code means the request rate exceeded the provisioned RU/s, triggering throttling.
• Q2 (429 Throttling Error): A. Improving partition key distribution to avoid hot partitions, or increasing provisioned RU/s — Better partition key distribution and/or higher provisioned throughput both help reduce 429 throttling errors.

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DP-420: Designing and Implementing Cloud-Native Applications Using Microsoft Azure Cosmos DB — term detail page