Indexing, in the simplest terms, is a way of sorting a set of data records. Without indexes, Azure Cosmos DB will have to scan every single item in the collection to look for the data- an operation that consumes time and resources. Indexing optimizes how Azure Cosmos DB stores and retrieves data.
Index Types in Azure Cosmos DB
Azure Cosmos DB supports two types of indexes- Range index and Spatial index.
Range Index
A range index is used for queries involving equality, range, and order by operations. These indexes are the default index type in Azure Cosmos DB and support numbers, strings, and Boolean data types. They can also be used for sorting data in ascending and descending orders.
Spatial Index
A spatial index is used for queries that involve spatial data. Spatial data refers to geographical data or data that has a geometric aspect. This kind of index allows the use of spatial functions and spatial queries in your Cosmos DB.
Choosing the Right Index Type for your Application
The type of index you choose depends mainly on the type of data your application handles and the type of queries you intend to run.
Range Index
Opt for a range index if your application makes frequent use of equality (=), inequality (<, >, <=, >=), and ‘ORDER BY’ queries. For instance, if your application maintains a list of products along with their prices and frequently searches products within a specific price range, a range index would be the right choice.
Spatial Index
If your application deals with geography-based data, spatial indexes would be more suitable. For instance, if your application helps users find restaurants in a specific area, spatial indexing would accelerate such queries by focusing on a certain ‘region’ of data.
Customizing Index Policies
As of now, we have been discussing default indexing in Azure Cosmos DB, but it’s essential to know that you can also customize indexing policies based on your application’s needs. This allows us to include or exclude certain paths, pick the index type, and control the index precision.
{
"indexingMode": "consistent",
"automatic": true,
"includedPaths": [
{"path": "/*", "indexes": [
{"kind": "Range", "dataType": "Number", "precision": -1},
{"kind": "Range", "dataType": "String", "precision": -1}
]}
],
"excludedPaths": [
{"path": "/\"systemMetadata\"/*"}
]
}
In the above example, all the numeric and string paths are included in the range type indexing, and the ‘systemMetadata’ path is excluded from the index.
In conclusion, nailing down the right index type can be crucial for the performance of your application. Range and Spatial indexes cater to different sorts of data, and customizing your index policies allows you to create a more efficient and high-performing database for your application. Considering your data type and query needs would guide you in selecting the suitable index type when designing and implementing native applications using Microsoft Azure Cosmos DB.
Practice Test
True or False: There are only two types of indexes in Azure Cosmos DB: primary and secondary.
– 1) True
– 2) False
Answer: False
Explanation: Azure Cosmos DB supports both automatic and manual indexing, and has multiple index types like Hash, Range, Spatial, and Composite.
Single Select: The ______ index type is used when we need to sort the data in Azure Cosmos DB.
– a) Hash
– b) Range
– c) Spatial
– d) Composite
Answer: b. Range
Explanation: The Range index type is ideal for sorting data. It supports efficient queries for ranges, as well as equality, and it’s the default for strings and numbers.
True or False: Hash index type in Azure Cosmos DB is used for efficient execution of range queries.
– 1) True
– 2) False
Answer: False
Explanation: Hash index type is used for equality comparisons and it doesn’t support efficient execution of range queries. Range index type is used for range queries.
Multiple Select: Which of the following index types support geospatial data in Azure Cosmos DB?
– a) Hash
– b) Range
– c) Spatial
– d) Composite
Answer: c. Spatial
Explanation: The Spatial index type is specifically designed to support geospatial data.
Single Select: When defining the indexing policy in Azure Cosmos DB, you must specify the ___________.
– a) Index type
– b) Indexing mode
– c) Indexing path
– d) All of the above
Answer: d. All of the above
Explanation: While defining the indexing policy, you need to specify index type, indexing mode (automatic or manual), and indexing path.
True or False: Composite indexing in Azure Cosmos DB improves the performance of queries that sort by multiple properties.
– 1) True
– 2) False
Answer: True
Explanation: Composite indexes improve the performance of queries that sort on more than one property or filter on multiple properties.
Single Select: Azure Cosmos DB uses _______ index for JSON values by default.
– a) Hash
– b) Range
– c) Spatial
– d) Composite
Answer: b. Range
Explanation: By default, Azure Cosmos DB uses Range indexes for all JSON values for efficient query processing.
Multiple Select: Which of the following can be optimized by using composite indexes in Azure Cosmos DB?
– a) Equality queries
– b) Range queries
– c) Sort operations
– d) Geospatial queries
Answer: a. Equality queries, b. Range queries, c. Sort operations
Explanation: Composite indexes can optimize equality queries, range queries, and sort operations, but they do not optimize geospatial queries.
True or False: In Azure Cosmos DB, you can only have one active indexing policy per container.
– 1) True
– 2) False
Answer: True
Explanation: Only one indexing policy can be active for a given container in Azure Cosmos DB.
Single Select: ______ index type is efficient for equality comparisons in Azure Cosmos DB.
– a) Hash
– b) Range
– c) Spatial
– d) Composite
Answer: a. Hash
Explanation: The Hash index type is efficient for presise equality comparisons. It provides constant-time comparisons but cannot be used for range comparisons.
Interview Questions
What are the two types of indexing available in Azure Cosmos DB?
The two types of indexing available in Azure Cosmos DB are Range and Spatial.
When should you choose the Range indexing policy in Azure Cosmos DB?
You should choose the Range indexing policy when you need to perform range-based operations on your data, for example sorting data in ascending or descending order.
What type of indexing should you use if you need to perform proximity queries on geospatial data types?
If you need to perform proximity queries on geospatial data types, you should use Spatial indexing.
What type of indexing is applied by default when a new container is created in Azure Cosmos DB?
When a new container is created in Azure Cosmos DB, Range indexing is applied by default.
How does a Composite index in Azure Cosmos DB benefit query performance?
A Composite index in Azure Cosmos DB benefits query performance by allowing multiple properties within a single item to be used in a sort operation, reducing the need for cross-partition queries and providing a significant performance improvement.
What should you consider when choosing an indexing policy in Azure Cosmos DB?
When choosing an indexing policy in Azure Cosmos DB, you should consider the nature of your workload, including the types of queries you will be running, the size, and the shape of your data.
Are there any additional costs associated with using indexes in Azure Cosmos DB?
Yes, indexes in Azure Cosmos DB consume storage space which can lead to additional costs. Also, when you perform read and write operations, these operations consume a certain amount of Request Units (RUs), which also incur costs.
Can you change the indexing policy of an existing container in Azure Cosmos DB?
Yes, you can change the indexing policy of an existing container in Azure Cosmos DB at any time without any downtime.
What is an indexing directive in Azure Cosmos DB?
An indexing directive in Azure Cosmos DB is an instruction you provide to the Azure Cosmos DB service about how to handle indexing for that particular write operation.
When should you use a Sparse index in Azure Cosmos DB?
Use a Sparse index in Azure Cosmos DB when the indexed data is unevenly distributed, with long stretches of unoccupied space, or when only very few properties need to be indexed, as it offers efficient storage utilization and query performance.
What is the impact of disabling indexing on a container in Azure Cosmos DB?
Disabling indexing on a container in Azure Cosmos DB means that you won’t be able to perform any queries on that container, but the read and write throughput will be higher and the cost will be less compared to a container with indexing.
Can you exclude certain properties from being indexed in Azure Cosmos DB?
Yes, you can exclude specific properties from being indexed in Azure Cosmos DB by setting the “excludedPaths” in your indexing policy strategy.
What is the default indexing mode in Azure Cosmos DB?
The default indexing mode in Azure Cosmos DB is Consistent, which means that the index is updated synchronously as data is written into the database.
Can spatial indexing be used on properties of Array data type in Azure Cosmos DB?
No, spatial indexing in Azure Cosmos DB only supports properties of type Point, Polygon, and LineString. It does not support properties of Array data types.
If you require case-sensitive SQL queries, which type of indexing should you use in Azure Cosmos DB?
If you require case-sensitive SQL queries, you should use Range indexing. Then, you need to set the “indexingPolicy” to “caseSensitive” and set it to true.
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