Declarative approach essentially describes what the program should accomplish, without necessarily stating how it should achieve the result. SQL, HTML, and CSS are examples of declarative languages. In contrast, imperative programming details the steps the program must take to reach a desired state or result. This might involve a series of statements, commands, or loops. Examples of imperative languages include Java, C++, and Python.
Let’s explore both approaches specifically in relation to the Azure Cosmos DB.
Declarative Operations
Declarative operations in Cosmos DB define what to do but not how to do it. SQL API, one of the core APIs offered by Cosmos DB, allows you to interact with your data in a declarative manner. With SQL API, you can declaratively query your data, without having to specify how the query will retrieve this data from the underlying JSON documents.
Let’s look at an example of a declarative query in SQL API:
SELECT * FROM c WHERE c.name=”John Doe”
In this query, we are declaring what we want: all documents where the ‘name’ property is “John Doe”. We do not specify how to go about retrieving this data – that’s handled by Cosmos DB engine itself, specifically, SQL API.
Imperative Operations
On the other hand, imperative operations in Azure Cosmos DB, detail the step-by-step procedure the operation must follow to achieve a certain result. Stored procedures, triggers, and user-defined functions (UDFs) in Cosmos DB are written using JavaScript, employing an imperative programming model.
For instance, consider the below JavaScript function for a stored procedure:
function updateDocument(docId, updatedDoc) {
var context = getContext();
var container = context.getCollection();
var accepted = container.replaceDocument(docId, updatedDoc,
function (err, docReplaced) {
if (err) throw new Error(‘Error’ + err.message);
context.getResponse().setBody(‘Document updated successfully’);
});
if (!accepted) throw new Error(‘Unable to update document, abort ‘);
}
This stored procedure details out the series of steps to find a particular document using its id ‘docId’ and replace it with the ‘updatedDoc’. Each step, along with error handling, is explicitly described in this function.
Choosing Declarative vs. Imperative
Selection between the two is largely influenced by your specific use-case. If you want a high level of control and are dealing with logic that demands stepwise execution, imperative operations could be preferred. On the contrary, if you’re dealing with queries where you only care about the result and not on the process of fetching it, declarative operations would be a better choice.
Here is a quick comparison between the two for more clarity:
| Declarative Operations | Imperative Operations | |
|---|---|---|
| Approach | What to do | How to do |
| Control | Low level of control | High level of control |
| Complexity | Low complexity | High complexity |
| Speed | Generally faster | Generally slower |
| Manageability | Easier to manage | Harder to manage |
| Example | SQL API | Stored Procedures |
To summarize, when designing applications for Azure Cosmos DB for the exam DP-420, understanding when to employ declarative versus imperative operations can make a significant difference in your program’s performance, manageability, and ease of development. Evaluate your scenario, understand the trade-offs, and choose the appropriate approach accordingly.
Practice Test
Is Cosmos DB a relational database within Microsoft Azure that uses SQL for all data transactions?
- True
- False
Answer: False
Explanation: Cosmos DB is a multi-model database service in Microsoft Azure, not a relational database. It accommodates various types of databases, including key-value, column-family, document-oriented, and graph.
Declarative operations in Cosmos DB are typically faster than imperative operations.
- True
- False
Answer: False
Explanation: Declarative operations generally introduce higher latencies than imperative operations. They are more suitable for less time-constrained tasks.
In a declarative operation, you specify the “what” but not the “how”.
- True
- False
Answer: True
Explanation: Declarative operations focus on the end result rather than providing step-by-step directives on how to achieve it.
Which type of operation is more prone to side effects?
- Declarative operations
- Imperative operations
Answer: Imperative operations
Explanation: As imperative operations involve providing a step-by-step process to achieve the desired result, it is more likely to result in side effects.
Imperative operations are generally best for handling complex queries and transactions.
- True
- False
Answer: True
Explanation: Imperative operations provide more control and flexibility making them better for handling complex queries and transactions.
Declarative operations are beneficial for solving real-time problems.
- True
- False
Answer: False
Explanation: Declarative operations, which involve focusing on the end result, are not necessarily the best choice for real-time problem-solving, as they may introduce latency.
Declarative operations are much easier to parallelize than Imperative operations.
- True
- False
Answer: True
Explanation: Declarative operations only concern with the desired outcome, not the execution process, which makes it easier to parallelize.
When should you prefer imperative operations over declarative operations?
- When the task has high latency requirements
- When the task has low latency requirements
Answer: When the task has low latency requirements
Explanation: Imperative operations typically have less latency, making them suitable for tasks requiring faster response times.
Declarative operations make the code more readable and understandable.
- True
- False
Answer: True
Explanation: Declarative operations focus on the “what” rather than the “how”, making the code more readable and understandable.
Imperative operations are generally a better choice for batch processing.
- True
- False
Answer: False
Explanation: Since imperative operations otherwise introduce higher latencies due to detailed step-by-step instruction, they aren’t usually the best choice for batch processing. Declarative operations might be better due to their ability to parallelize.
From a testing and debugging perspective, which operations are easier to handle?
- Declarative operations
- Imperative operations
Answer: Imperative operations
Explanation: From a testing and debugging perspective, imperative operations are typically easier to handle because they involve a step-by-step process that you can inspect at each stage.
Which tasks can declarative operations in Microsoft Azure Cosmos DB handle more effectively?
- Complex queries
- Data manipulation
- Bulk operations
Answer: Bulk operations
Explanation: Azure Cosmos DB offers declarative and bulk APIs for dealing with large amounts of data, making it a good choice for bulk operations.
Should databases be designed with a preference for either imperative or declarative operations?
- True
- False
Answer: False
Explanation: No single type of operation is universally superior. The choice between imperative and declarative operations depends on the specific use case and requirements.
Which operation type allows for better automation?
- Declarative operations
- Imperative operations
Answer: Declarative operations
Explanation: Declarative operations, which define the desired outcome without specifying how to reach it, are generally more conducive to automation.
The use of imperative operations can lead to high resource usage.
- True
- False
Answer: True
Explanation: Because imperative operations involve providing explicit instructions for every task, they can lead to high resource usage, especially for complex tasks.
Interview Questions
What is the difference between declarative and imperative operations in software development?
Declarative operations define the outcome without specifying how to achieve it. On the other hand, imperative operations provide a sequence of commands that describe how to reach the desired outcome.
In what context would one use imperative operations while working with Cosmos DB?
Imperative operations would be used while working with Cosmos DB when the developer wants direct control over the execution flow. This could include operations such as adding or updating specific database items, looping through data, or handling exceptions.
When should you use a declarative approach in Cosmos DB?
A declarative approach should be used in Cosmos DB when you want to focus on the “what” rather than the “how”. This is best used in scenarios like data modeling, where you define your data structures and relationships rather than manually manipulating the data.
What type of operation (imperative or declarative) is SQL API in Cosmos DB?
The SQL API in Cosmos DB is mostly declarative as it allows you to express what data you need without needing to detail how to retrieve it.
Which is generally more flexible, declarative or imperative operations?
Imperative operations are generally more flexible because they allow more direct control over the execution flow. They can handle more complex logic and custom scenarios that a declarative approach might not cater to.
Does Azure Cosmos DB support both types of operations?
Yes, Azure Cosmos DB supports both declarative and imperative operations. It provides a SQL API for declarative operations and supports stored procedures and triggers for imperative operations.
Can you provide an example of an imperative command in Azure Cosmos DB?
Yes, writing a stored procedure in Cosmos DB where you can directly control the flow of the program and manipulate the data with sequential steps is an example of an imperative command.
When should you avoid using imperative operations in Cosmos DB?
You should avoid using imperative operations while performing batch processing or operations that can be accomplished via SQL API because they often result in more complexity and less efficient performance.
Is it correct that only imperative operations can perform transactions in Cosmos DB?
No, it’s not correct. Both declarative and imperative operations can perform transactions in Cosmos DB. Declarative operations perform automatic transactions over all the data in the operation, while imperative operations perform transactions within stored procedures and triggers.
Can both declarative and imperative operations work together in Cosmos DB?
Yes, both declarative and imperative operations can work together in Cosmos DB. Imperative actions and logic can invoke declarative commands to retrieve, manage, and manipulate data.
What are the benefits of using declarative operations in Cosmos DB?
Declarative operations in Cosmos DB simplify the development process, provide automatic transaction management, and enhance performance for common database tasks.
How do declarative operations improve performance in Cosmos DB?
Declarative operations in Cosmos DB improve performance by reducing resource usage. They abstract the underlying implementation details and automatically optimize the execution plan for any given query.
How does using imperative operations affect debugging in Cosmos DB?
Imperative operations in Cosmos DB often lead to a more complex codebase which can potentially complicate the debugging process. With a well-documented and well-designed declarative process, debugging can become easier.
Is it better to use imperative operations in all scenarios in Cosmos DB?
No, it is not better to use imperative operations in all scenarios. The choice between imperative and declarative operations depends on the specific use case and the complexity associated. In general, using declarative operations is advised as it provides a simpler and error-resistant mechanism.
How should a developer decide between using declarative or imperative operations?
A developer should consider factors such as the specific use case, complexity of the task, the need for direct control over the program flow, and performance considerations. These factors should drive the choice between using declarative or imperative operations.
extutorials.com