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Use blob index tags to manage and find data with Go

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This article shows how to use blob index tags to manage and find data using the Azure Storage client module for Go.

Prerequisites

Set up your environment

If you don't have an existing project, this section shows how to set up a project to work with the Azure Blob Storage client module for Go. The steps include module installation, adding import paths, and creating an authorized client object. For details, see Get started with Azure Blob Storage and Go.

Install modules

Install the azblob module using the following command:

go get github.com/Azure/azure-sdk-for-go/sdk/storage/azblob

To authenticate with Microsoft Entra ID (recommended), install the azidentity module using the following command:

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

Add import paths

In your code file, add the following import paths:

import (
    "github.com/Azure/azure-sdk-for-go/sdk/azidentity"
	"github.com/Azure/azure-sdk-for-go/sdk/storage/azblob"
)

Some code examples in this article might require additional import paths. For specific details and example usage, see Code samples.

Create a client object

To connect an app to Blob Storage, create a client object using azblob.NewClient. The following example shows how to create a client object using DefaultAzureCredential for authorization:

func getServiceClientTokenCredential(accountURL string) *azblob.Client {
    // Create a new service client with token credential
    credential, err := azidentity.NewDefaultAzureCredential(nil)
    handleError(err)

    client, err := azblob.NewClient(accountURL, credential, nil)
    handleError(err)

    return client
}

Authorization

The authorization mechanism must have the necessary permissions to work with blob index tags. For authorization with Microsoft Entra ID (recommended), you need Azure RBAC built-in role Storage Blob Data Owner or higher. To learn more, see the authorization guidance for Get Blob Tags, Set Blob Tags, or Find Blobs by Tags.

About blob index tags

Blob index tags categorize data in your storage account using key-value tag attributes. These tags are automatically indexed and exposed as a searchable multi-dimensional index to easily find data. This article shows you how to set, get, and find data using blob index tags.

Blob index tags aren't supported for storage accounts with hierarchical namespace enabled. To learn more about the blob index tag feature along with known issues and limitations, see Manage and find Azure Blob data with blob index tags.

Set tags

You can set index tags if your code has authorized access to blob data through one of the following mechanisms:

For more information, see Setting blob index tags.

You can set tags by using the following method:

The tags specified in this method replace any existing tags. If existing values must be preserved, they must be downloaded and included in the call to this method. The following example shows how to set tags:

func setBlobTags(client *azblob.Client, containerName string, blobName string) {
    // Reference the blob as a client object
    blobClient := client.ServiceClient().NewContainerClient(containerName).NewBlobClient(blobName)

    // Get existing tags for the blob if they need to be preserved
    resp, err := blobClient.GetTags(context.TODO(), nil)
    handleError(err)
    tags := make(map[string]string)
    for _, v := range resp.BlobTags.BlobTagSet {
        tags[*v.Key] = *v.Value
    }

    // Add or modify blob tags
    var updated_tags = make(map[string]*string)
    updated_tags["tag1"] = to.Ptr("value1")
    updated_tags["tag2"] = to.Ptr("value2")

    // Combine existing tags with new tags
    for k, v := range updated_tags {
        tags[k] = *v
    }

    // Set blob tags
    _, err = blobClient.SetTags(context.TODO(), tags, nil)
    handleError(err)
}

You can remove all tags by calling SetTags with no tags, as shown in the following example:

func clearBlobTags(client *azblob.Client, containerName string, blobName string) {
    // Reference the blob as a client object
    blobClient := client.ServiceClient().NewContainerClient(containerName).NewBlobClient(blobName)

    // Clear blob tags
    _, err := blobClient.SetTags(context.TODO(), make(map[string]string), nil)
    handleError(err)
}

Get tags

You can get index tags if your code has authorized access to blob data through one of the following mechanisms:

For more information, see Getting and listing blob index tags.

You can get tags by using the following method:

The following example shows how to retrieve and iterate over the blob's tags:

func getBlobTags(client *azblob.Client, containerName string, blobName string) {
    // Reference the blob as a client object
    blobClient := client.ServiceClient().NewContainerClient(containerName).NewBlobClient(blobName)

    // Get the blob tags
    resp, err := blobClient.GetTags(context.TODO(), nil)
    handleError(err)

    // Print the blob tags
    for _, v := range resp.BlobTags.BlobTagSet {
        fmt.Printf("Key: %v, Value: %v\n", *v.Key, *v.Value)
    }
}

Filter and find data with blob index tags

You can use index tags to find and filter data if your code has authorized access to blob data through one of the following mechanisms:

For more information, see Finding data using blob index tags.

Note

You can't use index tags to retrieve previous versions. Tags for previous versions aren't passed to the blob index engine. For more information, see Conditions and known issues.

You can filter blob data based on index tags by using the following method:

The following example finds and lists all blobs tagged as an image:

func findBlobsByTags(client *azblob.Client, containerName string, blobName string) {
    // Reference the container as a client object
    containerClient := client.ServiceClient().NewContainerClient(containerName)

    // Filter blobs by tags
    where := "\"Content\"='image'"
    opts := container.FilterBlobsOptions{MaxResults: to.Ptr(int32(10))}
    resp, err := containerClient.FilterBlobs(context.TODO(), where, &opts)
    handleError(err)

    // Print the blobs found
    for _, blobItem := range resp.FilterBlobSegment.Blobs {
        fmt.Printf("Blob name: %v\n", *blobItem.Name)
    }
}

Note

The code samples in this guide are intended to help you get started with Azure Blob Storage and Go. You should modify error handling and Context values to meet the needs of your application.

Resources

To learn more about how to use index tags to manage and find data using the Azure Blob Storage client library for Go, see the following resources.

Code samples

REST API operations

The Azure SDK for Go contains libraries that build on top of the Azure REST API, allowing you to interact with REST API operations through familiar Go paradigms. The client library methods for managing and using blob index tags use the following REST API operations:

Client module resources

See also