Develop a design by storing multiple entity types in the same container

In Azure Cosmos DB, containers serve as a fundamental unit of scalability. These are schema-agnostic, meaning they can store items with diverse schemas. Each container is associated with a unique partition key that chooses the property of the items in the container. Partitioning ensures that data is evenly distributed across various partitions.

The decision to store multiple entity types in the same container stems from these characteristics of Cosmos DB containers and helps in optimizing the use of resources.

Designing for Multiple Entity Types in Same Container

While integrating multiple entity types in your Azure Cosmos DB, one primary concern is that Azure Cosmos DB is schema-less. This means that all records, albeit of different entity types, will merge into the same collection.

To differentiate between entity types, adopt a straightforward approach by creating a “type” attribute for your records. For example, if you have a ‘Person’ type and a ‘Company’ type, add a type attribute to each document:

{
“type”: “Person”,
“firstName”: “John”,
“lastName”: “Doe”
}
{
“type”: “Company”,
“companyName”: “TechCo”,
“location”: “New York”
}

The “type” attribute clarifies the kind of document at a glance, making it easy to query specific data.

To retrieve all persons from the container, your SQL query would look like this:

SELECT * FROM c WHERE c.type = “Person”

Implementing this model in your applications not only allows for optimum utilization of resources but also builds the ground for efficient querying and data retrieval.

Benefits of Storing Multiple Entity Types

• Reduced RU consumption: By querying a single container instead of multiple containers, you decrease the overall Request Unit (RU) consumption. Thus, this approach helps optimize costs associated with Azure Cosmos DB operations.
• Data co-location: Storing related types in the same container foments a co-location of data easing complex joins and transactions.
• Scalability: Cosmos DB automatically scales out once you provide a partition key. By storing multiple entities, you can effectively scale your application as documents of a type grow.

Tips for Implementing Multiple Entity Types in Azure Cosmos DB

When storing different entity types in the same container, remember:

• Use consistent partition keys: For the best scalability, ensure all item types use the same property for the partition key value.
• Maintain related data together: Where relations between items exist, maintain these items together in the same container. This facilitates querying and transaction processing.
• Use the Type property to differentiate items: To query items more efficiently, adopt a ‘Type’ property to the item body to differentiate between types.

Designing and implementing native applications using Microsoft Azure Cosmos DB involves many strategies. Storing multiple entity types in the same container is one such effective method, which considerably optimizes database costs and scales with each kind of document growth. The key is to design thoughtfully based on the requirements and the relations between your data models.

Practice Test

True/False: You can store multiple entity types in the same container within Microsoft Azure Cosmos DB.

• True
• False

Answer: True

Explanation: Microsoft Azure Cosmos DB allows storing multiple entity types in the same container which promotes storage efficiency.

Multiple select: Which of the following are benefits of storing multiple entity types in the same container within Microsoft Azure Cosmos DB?

• a) Reduced resource use
• b) Simplified queries
• c) Increased data consistency
• d) Improved scalability

Answer: a) Reduced resource use, c) Increased data consistency, d) Improved scalability

Explanation: Storing multiple entity types in the same container can decrease resource use, improve data consistency and scalability. However, it may not always simplify queries as it may require additional filtering to get specific entity types.

True/False: Different entity types in the same container can have different partition keys.

• True
• False

Answer: False

Explanation: In Microsoft Azure Cosmos DB, all entities within the same container need to have the same partition key.

Single select: What type of data modeling does Azure Cosmos DB support?

• a) Document data
• b) Column data
• c) Both document and column data

Answer: c) Both document and column data

Explanation: Microsoft Azure Cosmos DB is a globally distributed, multi-model database service. It supports both document and column data.

True/False: Storing multiple entity types in the same container can facilitate transactions across these entities.

• True
• False

Answer: True

Explanation: Since Azure Cosmos DB supports transactions within a single partition, having multiple entities in the same container (and hence in the same partition) enables transactional operations across these entities.

Single select: Which of the following is a key challenge in storing multiple entities in the same container?

• a) Filtering data
• b) Data inconsistency
• c) Scalability issues
• d) All of the above

Answer: a) Filtering data

Explanation: Storing different entities in one container could increase the complexity in filtering data.

True/False: The schema within a container in Cosmos DB is flexible, allowing multiple entity types to be stored together.

• True
• False

Answer: True

Explanation: Cosmos DB uses schema-agnostic indexing where you don’t have to deal with schema or index management, making it suitable to store multiple entity types together.

Multiple select: What does Cosmos DB use to distribute data and traffic evenly across partitions?

• a) Partition Key
• b) Request Unit
• c) Throughput
• d) Entity Types

Answer: a) Partition Key, c) Throughput

Explanation: Partition Key in Cosmos DB is used to distribute data evenly across all partitions. Throughput, which is measured in Request Units, is also distributed across these partitions to accommodate traffic.

Single select: What is the maximum storage limit per partition in Azure Cosmos DB?

• a) 10 GB
• b) 20 GB
• c) 50 GB
• d) 100 GB

Answer: b) 20 GB

Explanation: Each partition in Cosmos DB has a maximum limit of 20 GB of storage.

True/False: It is not possible to perform transactional operations across multiple containers in Cosmos DB.

• True
• False

Answer: True

Explanation: Transactions in Cosmos DB are scoped to a single logical partition. Therefore, transactional operations are not possible across multiple containers.

Interview Questions

1. How can you develop a design by storing multiple entity types in the same container in Azure Cosmos DB?

You can achieve this by using a property called “discriminator” in the JSON documents to differentiate between entity types.

2. What is the purpose of using a discriminator property when storing multiple entity types in the same container?

The discriminator property helps Azure Cosmos DB to infer the type of the document and allows for differentiating between entity types.

3. Can you have different indexing policies for each entity type stored in the same container?

Yes, you can define different indexing policies for each entity type in a container to optimize performance.

4. How can you query for a specific entity type within a container that stores multiple entity types?

You can use the discriminator property in the WHERE clause of a SQL query to filter documents based on their entity type.

5. Is it possible to have different partition keys for each entity type within the same container?

No, all entities stored in the same container must have the same partition key.

6. How does Azure Cosmos DB handle performance when storing multiple entity types in the same container?

Azure Cosmos DB automatically optimizes performance by partitioning data based on the chosen partition key.

7. What is the recommended approach for designing a schema when storing multiple entity types in the same container?

It is recommended to have a well-defined schema that includes a discriminator property to differentiate between entity types.

8. Can you update the schema of a container that stores multiple entity types without impacting existing data?

Yes, you can update the schema of a container without affecting existing data by adding new properties or changing indexing policies.

9. How does Azure Cosmos DB handle scalability when storing multiple entity types in the same container?

Azure Cosmos DB automatically scales out based on the chosen partition key to ensure high performance and availability.

10. What are the benefits of storing multiple entity types in the same container in Azure Cosmos DB?

Some benefits include reduced complexity, simplified data management, and improved query performance.

11. Can you store hierarchical data structures within a container that stores multiple entity types?

Yes, you can store nested JSON documents to represent complex hierarchical data structures within a container.

12. How can you enforce data validation rules for different entity types stored in the same container?

You can implement custom validation logic in your application code to ensure data integrity and enforce business rules.

13. Is it recommended to denormalize data when storing multiple entity types in the same container?

Denormalizing data can improve query performance, but you should carefully consider the trade-offs between denormalization and data consistency.

14. How can you maintain data consistency when updating multiple entity types within the same container?

You can use transactions or implement optimistic concurrency control to ensure data consistency when updating multiple entity types.

15. Can you mix different consistency levels for each entity type stored in the same container?

No, the consistency level is defined at the container level and applies to all documents within that container.