MetaSearch

The following code provides an example of how to enable the metadata management feature for a specified bucket. After you enable this feature, OSS creates a metadata index library for the bucket and creates metadata indexes for all objects stored within. After the metadata index library is created, OSS continues to perform quasi-real-time scans on incremental objects in the bucket and creates metadata indexes for the incremental objects.

package main

import (
	"context"
	"flag"   
	"log"     

	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss"          
	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss/credentials" 
)

var (
	region     string // Specify a variable to store the region information obtained from the command lines.
	bucketName string // Specify a variable to store the bucket name obtained from the command lines.
)

// The init function is executed before the main function to initialize the program.
func init() {
	// Use a command line parameter to specify the region.
	flag.StringVar(&region, "region", "", "The region in which the bucket is located.")
	// Use a command line parameter to specify the bucket name.
	flag.StringVar(&bucketName, "bucket", "", "The name of the bucket.")
}

func main() {
	flag.Parse() // Parse command line parameters.

	// Check if the bucket name is specified. If not, the program outputs default parameters and terminates.
	if len(bucketName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, bucket name required") // Log the error message and terminate the program.
	}

	// Check whether the region is specified. If the region is not specified, output the default parameters and exit the program.
	if len(region) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, region required") // Log the error message and terminate the program.
	}

	// Create and configure a client and use environment variables to pass the credential provider.
	cfg := oss.LoadDefaultConfig().
		WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
		WithRegion(region)

	client := oss.NewClient(cfg) // Use the client configurations to create a new OSSClient instance.

	// Create an OpenMetaQuery request to enable the metadata management feature for a specific bucket.
	request := &oss.OpenMetaQueryRequest{
		Bucket: oss.Ptr(bucketName), // Specify the name of the bucket.
	}
	result, err := client.OpenMetaQuery(context.TODO(), request) // Execute the request to enable the metadata management feature for the bucket.
	if err != nil {
		log.Fatalf("failed to open meta query %v", err) // If an error occurs, record the error message and terminate the program.
	}

	log.Printf("open meta query result:%#v\n", result) // Display the result.
}

The following code provides an example of how to query information about the metadata index library of a bucket.

package main

import (
	"context" 
	"flag"   
	"log"   

	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss"
	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss/credentials"
)

var (
	region     string // Specify a variable to store the region information obtained from the command lines.
	bucketName string // Specify a variable to store the bucket name obtained from the command lines.
)

// The init function is executed before the main function to initialize the program.
func init() {
	// Use a command line parameter to specify the region.
	flag.StringVar(&region, "region", "", "The region in which the bucket is located.")
	// Use a command line parameter to specify the bucket name.
	flag.StringVar(&bucketName, "bucket", "", "The name of the bucket.")
}

func main() {
	flag.Parse() // Parse command line parameters.

	// Check if the bucket name is specified. If not, the program outputs default parameters and terminates.
	if len(bucketName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, bucket name required") // Log the error message and terminate the program.
	}

	// Check if the region is specified. If not, the program outputs default parameters and terminates.
	if len(region) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, region required") // Log the error message and terminate the program.
	}

	// Create and configure a client and use environment variables to pass the credential provider and the region.
	cfg := oss.LoadDefaultConfig().
		WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
		WithRegion(region)

	client := oss.NewClient(cfg) // Create a new OSSClient instance.

	// Create a GetMetaQueryStatus request to query information about the metadata index library of a specific bucket.
	request := &oss.GetMetaQueryStatusRequest{
		Bucket: oss.Ptr(bucketName), // Specify the name of the bucket.
	}
	result, err := client.GetMetaQueryStatus(context.TODO(), request) // Execute the query request.
	if err != nil {
		log.Fatalf("failed to get meta query status %v", err) // If an error occurs, record the error message and terminate the program.
	}

	log.Printf("get meta query status result:%#v\n", result)
}

The following code provides an example of how to use MetaSearch to query the objects that meet specific conditions and list the object information based on specific fields and sorting methods.

package main

import (
	"context"
	"flag"
	"fmt"
	"log"

	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss"
	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss/credentials"
)

var (
	region     string // Specify a variable to store the region information obtained from the command lines.
	bucketName string // Specify a variable to store the bucket name obtained from the command lines.
)

// The init function is executed before the main function to initialize the program.
func init() {
	// Use a command line parameter to specify the region. By default, the parameter is an empty string.
	flag.StringVar(&region, "region", "", "The region in which the bucket is located.")
	// Use a command line parameter to specify the bucket name. By default, the parameter is an empty string.
	flag.StringVar(&bucketName, "bucket", "", "The name of the bucket.")
}

func main() {
	flag.Parse() // Parse command line parameters.

	// Check if the bucket name is specified. If not, the program outputs default parameters and terminates.
	if len(bucketName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, bucket name required")
	}

	// Check if the region is specified. If not, the program outputs default parameters and terminates.
	if len(region) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, region required")
	}

	// Create and configure a client and use environment variables to pass the credential provider and the region.
	cfg := oss.LoadDefaultConfig().
		WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
		WithRegion(region)

	client := oss.NewClient(cfg) // Use the client configurations to create a new OSSClient instance.

	// Create a DoMetaQuery request to query the objects that meet specific conditions.
	request := &oss.DoMetaQueryRequest{
		Bucket: oss.Ptr(bucketName), // Specify the name of the bucket.
		MetaQuery: &oss.MetaQuery{
			Query: oss.Ptr(`{"Field": "Size","Value": "1048576","Operation": "gt"}`), // Query objects whose size is larger than 1 MB.
			Sort:  oss.Ptr("Size"),                                                  // List the objects by size.
			Order: oss.Ptr(oss.MetaQueryOrderAsc),                                  // Sort the objects in ascending order.
		},
	}
	result, err := client.DoMetaQuery(context.TODO(), request) // Execute the request to query the objects that meet the preceding conditions.
	if err != nil {
		log.Fatalf("failed to do meta query %v", err)
	}

	// Display the token used to query data on the next page.
	fmt.Printf("NextToken:%s\n", *result.NextToken)

	// Traverse the returned results and display the details of each object.
	for _, file := range result.Files {
		fmt.Printf("File name: %s\n", *file.Filename)
		fmt.Printf("size: %d\n", file.Size)
		fmt.Printf("File Modified Time:%s\n", *file.FileModifiedTime)
		fmt.Printf("Oss Object Type:%s\n", *file.OSSObjectType)
		fmt.Printf("Oss Storage Class:%s\n", *file.OSSStorageClass)
		fmt.Printf("Object ACL:%s\n", *file.ObjectACL)
		fmt.Printf("ETag:%s\n", *file.ETag)
		fmt.Printf("Oss CRC64:%s\n", *file.OSSCRC64)
		if file.OSSTaggingCount != nil {
			fmt.Printf("Oss Tagging Count:%d\n", *file.OSSTaggingCount)
		}

		// Display the tags of the objects.
		for _, tagging := range file.OSSTagging {
			fmt.Printf("Oss Tagging Key:%s\n", *tagging.Key)
			fmt.Printf("Oss Tagging Value:%s\n", *tagging.Value)
		}

		// Display the user metadata.
		for _, userMeta := range file.OSSUserMeta {
			fmt.Printf("Oss User Meta Key:%s\n", *userMeta.Key)
			fmt.Printf("Oss User Meta Key Value:%s\n", *userMeta.Value)
		}
	}
}

The following code provides an example of how to disable the metadata management feature for a specific bucket.

package main

import (
	"context"
	"flag"    
	"log"    

	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss"          
	"github.com/aliyun/alibabacloud-oss-go-sdk-v2/oss/credentials" 
)

var (
	region     string // Specify a variable to store the region information obtained from the command lines.
	bucketName string // Specify a variable to store the bucket name obtained from the command lines.
)

// The init function is executed before the main function to initialize the program.
func init() {
	// Use a command line parameter to specify the region.
	flag.StringVar(&region, "region", "", "The region in which the bucket is located.")
	// Use a command line parameter to specify the bucket name.
	flag.StringVar(&bucketName, "bucket", "", "The name of the bucket.")
}


func main() {
	flag.Parse() // Parse command line parameters.

	// Check if the bucket name is specified. If not, the program outputs default parameters and terminates.
	if len(bucketName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, bucket name required") // Log the error message and terminate the program.
	}

	// Check if the region is specified. If not, the program outputs default parameters and terminates.
	if len(region) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, region required") // Log the error message and terminate the program.
	}

	// Create and configure a client and use environment variables to pass the credential provider and the region.
	cfg := oss.LoadDefaultConfig().
		WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
		WithRegion(region)

	client := oss.NewClient(cfg) // Create a new OSSClient instance.

	// Create a CloseMetaQuery request to disable the metadata management feature for the bucket.
	request := &oss.CloseMetaQueryRequest{
		Bucket: oss.Ptr(bucketName), // Specify the name of the bucket.
	}
	result, err := client.CloseMetaQuery(context.TODO(), request) // Execute the request.
	if err != nil {
		log.Fatalf("failed to close meta query %v", err) // If an error occurs, record the error message and exit the program.
	}

	log.Printf("close meta query result:%#v\n", result)
}