Upsert operation refers to an action that inserts rows into a database table if they do not already exist, or updates them if they do. It’s a smart operation that can save time and simplify code.
Consider, for example, you have a batch of data you want to upload into a SQL database, but you’re not certain whether some of the data points are already in the database. You could attempt to insert all data and deal with error messages for duplicate keys, or write code to check for each data point before insertion. With upserting, however, you attempt to update the data, and if it doesn’t exist, then you insert it.
Microsoft Azure offers powerful support for upsert operations to effectively manage data, especially when dealing with Azure Cosmos DB or Azure SQL Databases.
Upsert capabilities in Azure Cosmos DB
Azure Cosmos DB offers native support for database upsert operations via the `.Upsert` method. This operation guarantees atomicity of the operation and replaces the entire document with new content, with only one trip to the server.
Here is a simple C# code snippet demonstrating how to perform an upsert in Azure Cosmos DB.
CosmosClient cosmosClient = new CosmosClient(“connection string”);
Database database = cosmosClient.GetDatabase(“database name”);
Container container = database.GetContainer(“container name”);
dynamic item = new
{
id = “some id”,
value = “some value”
};
ItemResponse<dynamic> response = await container.UpsertItemAsync(item, new PartitionKey(item.id));
Console.WriteLine(“Request charge of the operation: ” + response.RequestCharge);
Console.WriteLine(“StatusCode of the operation: ” + response.StatusCode);
In this example, an instance of `CosmosClient` is created first, then the appropriate database and container are selected. A new item is then defined – if the item with the specified id exists, it will be updated; if it does not, it will be inserted.
Azure SQL Database Upserts
In the context of an Azure SQL Database, you can utilize the `MERGE` statement to perform an Upsert operation. The `MERGE` statement merges data from a source table into a target table by specifying a condition that determines how to apply insert, update, or delete operations.
Let’s consider a simple example with a Student table. If a student ID already exists, we want to update the student’s name. If it doesn’t exist, we insert a new row.
MERGE INTO Student AS Target
USING (SELECT StudentID, StudentName FROM dbo.Student) AS Source
ON (Target.StudentID = Source.StudentID)
WHEN MATCHED THEN
UPDATE SET Target.StudentName = Source.StudentName
WHEN NOT MATCHED BY TARGET THEN
INSERT (StudentID, StudentName) VALUES (Source.StudentID, Source.StudentName)
In the above SQL statement, the ‘MERGE INTO Student AS Target’ indicates the targeted table. ‘USING (SELECT StudentID, StudentName FROM dbo.Student) AS Source’ specifies the source of data. If the source data matches the target data (Source.StudentID = Target.StudentID), the existing row is updated. If the source data is not found in the target, a new row is inserted.
Key Considerations
While upserting operations provide convenience and efficiency in handling data, keep in mind that they may have some performance implications. Therefore, understanding your database’s capability and choosing the right balance between update and insert operations is crucial. Upserting is extremely valuable and efficient, especially when dealing with large bulk operations.
As a candidate aspiring to clear the DP-203 Data Engineering on Microsoft Azure exam, understanding the nuances of performing upsert operations can prove to be a game-changer in managing data on Azure.
Practice Test
True or False: The term “upsert” refers to a combination of “update” and “insert”.
Answer: True
Explanation: Upsert is a combination of update and insert. It allows you to either update existing records or insert new records into a database table based on whether a matching record already exists.
Which of these are use cases for upsert operations?
- A. Integrate data from different sources.
- B. Eliminate duplicate records.
- C. Optimize read operations.
- D. None of the above.
Answer: A, B
Explanation: Upsert operations are used when integrating data from different sources or when reducing duplicate records in a table. They are not directly related to read operation optimization.
True or False: A MERGE statement can be used for doing upsert operations in Azure SQL Database.
Answer: True
Explanation: The MERGE statement, found in Azure SQL Database, provides a way to perform upsert operations by combining the sequences of conditional INSERT, UPDATE, and DELETE statements.
In Azure Table Storage, you can use ______ to upsert data.
- A. Replace
- B. InsertOrMerge
- C. Merge
- D. InsertOrReplace
Answer: D, InsertOrReplace
Explanation: In Azure Table Storage, you can use the InsertOrReplace operation to upsert data. This operation inserts the record when it doesn’t exist and replaces it when it does.
True or False: Upsert operations are not idempotent by default.
Answer: False
Explanation: Upsert operations are indeed idempotent by default, meaning that applying them multiple times will have the same effect as applying them once.
Which of these services support upsert operations in Microsoft Azure?
- A. Azure Cosmos DB
- B. Azure SQL Database
- C. Azure Data Lake Store
- D. Azure Data Warehouse
Answer: A, B
Explanation: Both Azure Cosmos DB and Azure SQL Database provide support for upsert operations, while the Azure Data Lake Store and Azure Data Warehouse do not.
True or False: Upsert operations can reduce the amount of code required for data modification queries.
Answer: True
Explanation: Because upsert operations can handle MISSING data or new data without writing separate queries, they can simplify your code.
______ statement is suitable for upsert operations in Azure Stream Analytics.
- A. UPDATE
- B. INSERT
- C. MERGE
- D. SELECT
Answer: C, MERGE
Explanation: Azure Stream Analytics doesn’t support upsert semantics natively. But you can achieve these using the MERGE statement by connecting your Stream Analytics job’s output to stored procedures.
True or False: Azure Data Explorer doesn’t provide support for upsert operations.
Answer: False
Explanation: Azure Data Explorer supports upsert by the ‘.ingest inline’ command combined with ‘update policy’.
When Azure Cosmos DB performs an upsert operation, it first reads the entire document before completing the write operation. This can affect ______.
- A. Storage
- B. Throughput
- C. Security
- D. Availability
Answer: B, Throughput
Explanation: Reading the entire document can consume some of your provisioned throughput, which could impact other operations. This does not affect your storage, security, or availability.
Interview Questions
What is the purpose of “Upsert” in regards to handling data?
“Upsert” is a smart operation used in data handling which updates existing records if a matching record exists, and inserts a new record if no matching record is found.
Which Azure services support the “Upsert” functionality?
Azure services such as Azure Cosmos DB, Azure SQL Database, and Azure Data Factory support the “Upsert” functionality.
In the context of Azure Cosmos DB, what is the syntax for an “Upsert” operation?
The syntax for an “Upsert” operation in Azure Cosmos DB is ‘UpsertDocumentAsync(Uri, Object, RequestOptions, Boolean)’.
What is significant about the third parameter in Azure Cosmos DB’s ‘UpsertDocumentAsync’ function?
The third parameter in ‘UpsertDocumentAsync’ is ‘RequestOptions’ which provides optional parameters to specify when calling an operation.
Does Azure SQL Database have a native “Upsert” command?
Azure SQL Database does not have a native “Upsert” command. However, the “Upsert” functionality can be achieved by using a combination of SQL operations like ‘IF EXISTS’ (to handle updates) and ‘IF NOT EXISTS’ (to handle inserts).
What is the name of the stored procedure command for implementing “Upsert” in Azure SQL Database?
‘Merge’ is the stored procedure command used to implement “Upsert” in Azure SQL Database.
In Azure Data Factory, which activity makes use of the “Upsert” operation during the data transformation process?
Azure Data Factory uses “Upsert” operation in ‘Copy Activity’ during the data transformation process within the ‘Sink’ section of the pipeline.
Is it possible to use “Upsert” with batch operations in Azure Cosmos DB?
Yes, “Upsert” operation can be used with batch operations in Azure Cosmos DB.
What does the addition of ‘Merge’ functionality in Azure SQL Data Warehouse indicate?
The addition of ‘Merge’ functionality in Azure SQL Data Warehouse indicates the introduction of “Upsert” capability.
Can “Upsert” be used in Azure Stream Analytics?
Yes, you can use Azure Stream Analytics to output “Upsert” and “Delete” commands to Azure SQL Database and Azure Cosmos DB.
What function does Upsert action serve in Azure IoT Hub?
In Azure IoT Hub, the “Upsert” action helps maintain the desired properties for a device twin, updating existing properties if they exist or creating them if they do not.
What is the significance of partition keys in the context of “Upsert” operations using Azure Cosmos DB?
Partition keys define the transaction scope for “Upsert” operations in Azure Cosmos DB. All documents involved in the transaction must share the same partition key.
Can “Upsert” operation be performed in an Azure Table storage?
Yes, the “Upsert” operation can be performed in Azure Table storage using ‘InsertOrReplace’ operation.
What is an important consideration while choosing the ‘Merge’ strategy for “Upsert” in an Azure SQL Database?
The ‘Merge’ operation may run slower if there is a large amount of data in the table, as performance depends on the indexes defined on the table.
Is there any throttling limit for “Upsert” operations in Azure Cosmos DB?
Yes, Azure Cosmos DB has a throttling threshold. If the number of “Upsert” operations exceeds the provisioned throughput, Azure Cosmos DB will throttle the operations and return ‘429’ status codes.
extutorials.com