Quickstart: Use Azure Cosmos DB for NoSQL with Azure SDK for Go

Article
12/06/2024
Applies to:

✅ NoSQL

In this quickstart, you deploy a basic Azure Cosmos DB for Table application using the Azure SDK for Go. Azure Cosmos DB for Table is a schemaless data store allowing applications to store structured table data in the cloud. You learn how to create tables, rows, and perform basic tasks within your Azure Cosmos DB resource using the Azure SDK for Go.

API reference documentation | Library source code | Package (Go) | Azure Developer CLI

Prerequisites

Azure Developer CLI
Docker Desktop
Go 1.21 or newer

If you don't have an Azure account, create a Trial before you begin.

Initialize the project

Use the Azure Developer CLI (azd) to create an Azure Cosmos DB for Table account and deploy a containerized sample application. The sample application uses the client library to manage, create, read, and query sample data.

Open a terminal in an empty directory.
If you're not already authenticated, authenticate to the Azure Developer CLI using azd auth login. Follow the steps specified by the tool to authenticate to the CLI using your preferred Azure credentials.
```
azd auth login
```

Use azd init to initialize the project.

azd init --template cosmos-db-nosql-go-quickstart

During initialization, configure a unique environment name.
Deploy the Azure Cosmos DB account using azd up. The Bicep templates also deploy a sample web application.
```
azd up
```
During the provisioning process, select your subscription, desired location, and target resource group. Wait for the provisioning process to complete. The process can take approximately five minutes.

Once the provisioning of your Azure resources is done, a URL to the running web application is included in the output.

Deploying services (azd deploy)

  (✓) Done: Deploying service web
- Endpoint: <https://[container-app-sub-domain].azurecontainerapps.io>

SUCCESS: Your application was provisioned and deployed to Azure in 5 minutes 0 seconds.

Use the URL in the console to navigate to your web application in the browser. Observe the output of the running app.

Screenshot of the running web application.

Install the client library

The client library is available through Go, as the azcosmos package.

Open a terminal and navigate to the /src folder.
```
cd ./src
```
If not already installed, install the azcosmos package using go install.
```
go install github.com/Azure/azure-sdk-for-go/sdk/data/azcosmos
```

Also, install the azidentity package if not already installed.

go install github.com/Azure/azure-sdk-for-go/sdk/azidentity

Open and review the src/go.mod file to validate that the github.com/Azure/azure-sdk-for-go/sdk/data/azcosmos and github.com/Azure/azure-sdk-for-go/sdk/azidentity entries both exist.

Object model

Name	Description
`CosmosClient`	This class is the primary client class and is used to manage account-wide metadata or databases.
`CosmosDatabase`	This class represents a database within the account.
`CosmosContainer`	This class is primarily used to perform read, update, and delete operations on either the container or the items stored within the container.
`PartitionKey`	This class represents a logical partition key. This class is required for many common operations and queries.

The sample code in the template uses a database named cosmicworks and container named products. The products container contains details such as name, category, quantity, a unique identifier, and a sale flag for each product. The container uses the /category property as a logical partition key.

Authenticate the client

This sample creates a new instance of CosmosClient using azcosmos.NewClient and authenticates using a DefaultAzureCredential instance.

credential, err := azidentity.NewDefaultAzureCredential(nil)
if err != nil {
    return err
}

clientOptions := azcosmos.ClientOptions{
    EnableContentResponseOnWrite: true,
}

client, err := azcosmos.NewClient("<azure-cosmos-db-nosql-account-endpoint>", credential, &clientOptions)
if err != nil {
    return err
}

Get a database

Use client.NewDatabase to retrieve the existing database named cosmicworks.

database, err := client.NewDatabase("cosmicworks")
if err != nil {
    return err
}

Get a container

Retrieve the existing products container using database.NewContainer.

container, err := database.NewContainer("products")
if err != nil {
    return err
}

Create an item

Build a Go type with all of the members you want to serialize into JSON. In this example, the type has a unique identifier, and fields for category, name, quantity, price, and sale.

type Item struct {
  Id        string  `json:"id"`
  Category  string  `json:"category"`
  Name      string  `json:"name"`
  Quantity  int     `json:"quantity"`
  Price     float32 `json:"price"`
  Clearance bool    `json:"clearance"`
}

Create an item in the container using container.UpsertItem. This method "upserts" the item effectively replacing the item if it already exists.

item := Item {
    Id:        "aaaaaaaa-0000-1111-2222-bbbbbbbbbbbb",
    Category:  "gear-surf-surfboards",
    Name:      "Yamba Surfboard",
    Quantity:  12,
    Price:     850.00,
    Clearance: false,
}

partitionKey := azcosmos.NewPartitionKeyString("gear-surf-surfboards")

context := context.TODO()

bytes, err := json.Marshal(item)
if err != nil {
    return err
}

response, err := container.UpsertItem(context, partitionKey, bytes, nil)
if err != nil {
    return err
}

Read an item

Perform a point read operation by using both the unique identifier (id) and partition key fields. Use container.ReadItem to efficiently retrieve the specific item.

partitionKey := azcosmos.NewPartitionKeyString("gear-surf-surfboards")

context := context.TODO()

itemId := "aaaaaaaa-0000-1111-2222-bbbbbbbbbbbb"

response, err := container.ReadItem(context, partitionKey, itemId, nil)
if err != nil {
    return err
}

if response.RawResponse.StatusCode == 200 {
    read_item := Item{}
    err := json.Unmarshal(response.Value, &read_item)
    if err != nil {
        return err
    }
}

Query items

Perform a query over multiple items in a container using container.NewQueryItemsPager. Find all items within a specified category using this parameterized query:

SELECT * FROM products p WHERE p.category = @category

partitionKey := azcosmos.NewPartitionKeyString("gear-surf-surfboards")

query := "SELECT * FROM products p WHERE p.category = @category"

queryOptions := azcosmos.QueryOptions{
    QueryParameters: []azcosmos.QueryParameter{
        {Name: "@category", Value: "gear-surf-surfboards"},
    },
}

pager := container.NewQueryItemsPager(query, partitionKey, &queryOptions)

Parse the paginated results of the query by looping through each page of results using pager.NextPage. Use pager.More to determine if there are any results left at the start of each loop.

items := []Item{}

for pager.More() {
    response, err := pager.NextPage(context.TODO())
    if err != nil {
        return err
    }

    for _, bytes := range response.Items {
        item := Item{}
        err := json.Unmarshal(bytes, &item)
        if err != nil {
            return err
        }
        items = append(items, item)
    }
}

Clean up resources

When you no longer need the sample application or resources, remove the corresponding deployment and all resources.

azd down