Query files using OSS SDK for Go 2.0

Usage notes

• The sample code in this topic uses the region ID cn-hangzhou of the China (Hangzhou) region. By default, the public endpoint is used to access resources in a bucket. If you want to access resources in the bucket by using other Alibaba Cloud services in the same region in which the bucket is located, use an internal endpoint. For more information about the regions and endpoints supported by OSS, see Regions and endpoints.

• In this topic, access credentials are obtained from environment variables. For more information about how to configure access credentials, see Configure access credentials.

• Querying files requires the oss:GetObject permission. For more information, see Grant custom permissions to a RAM user.

• OSS supports querying only CSV and JSON files.

Method definition

func (c *Client) SelectObject(ctx context.Context, request *SelectObjectRequest, optFns ...func(*Options)) (*SelectObjectResult, error)

Request parameters

Response parameters

Sample code

package main

import (
	"context"
	"flag"
	"io"
	"log"

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

// Define global variables.
var (
	region     string // The storage region.
	bucketName string // The bucket name.
	objectName string // The object name.
)

// The init function is used to initialize command line parameters.
func init() {
	flag.StringVar(&region, "region", "", "The region in which the bucket is located.")
	flag.StringVar(&bucketName, "bucket", "", "The name of the bucket.")
	flag.StringVar(&objectName, "object", "", "The name of the object.")
}

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

	// Check whether the bucket name is empty.
	if len(bucketName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, bucket name required")
	}

	// Check whether the region is empty.
	if len(region) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, region required")
	}

	// Check whether the object name is empty.
	if len(objectName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, object name required")
	}

	// Load the default configurations and set the credential provider and region.
	cfg := oss.LoadDefaultConfig().
		WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
		WithRegion(region)

	// Create an OSS client.
	client := oss.NewClient(cfg)

	// Create a request to select an object.
	request := &oss.SelectObjectRequest{
		Bucket: oss.Ptr(bucketName), // The bucket name.
		Key:    oss.Ptr(objectName), // The object name.
		SelectRequest: &oss.SelectRequest{
			Expression: oss.Ptr("select * from ossobject limit 10"), // Define an SQL expression to query the first 10 rows of data in the object.
			InputSerializationSelect: oss.InputSerializationSelect{
				CsvBodyInput: &oss.CSVSelectInput{
					FileHeaderInfo: oss.Ptr("Use"),
				},
			},
			OutputSerializationSelect: oss.OutputSerializationSelect{
				OutputHeader: oss.Ptr(true),
			},
		},
	}

	// Execute the request to select the object.
	result, err := client.SelectObject(context.TODO(), request)
	if err != nil {
		log.Fatalf("failed to select object %v", err)
	}

	content, err := io.ReadAll(result.Body)
	if err != nil {
		log.Fatalf("failed to read object %v", err)
	}

	// Print the result of selecting the object.
	log.Printf("select object result:%#v\n", string(content))
}

package main

import (
	"context"
	"flag"
	"io"
	"log"

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

// Define global variables.
var (
	region     string // The storage region.
	bucketName string // The bucket name.
	objectName string // The object name.
)

// The init function is used to initialize command line parameters.
func init() {
	flag.StringVar(&region, "region", "", "The region in which the bucket is located.")
	flag.StringVar(&bucketName, "bucket", "", "The name of the bucket.")
	flag.StringVar(&objectName, "object", "", "The name of the object.")
}

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

	// Check whether the bucket name is empty.
	if len(bucketName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, bucket name required")
	}

	// Check whether the region is empty.
	if len(region) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, region required")
	}

	// Check whether the object name is empty.
	if len(objectName) == 0 {
		flag.PrintDefaults()
		log.Fatalf("invalid parameters, object name required")
	}

	// Load the default configurations and set the credential provider and region.
	cfg := oss.LoadDefaultConfig().
		WithCredentialsProvider(credentials.NewEnvironmentVariableCredentialsProvider()).
		WithRegion(region)

	// Create an OSS client.
	client := oss.NewClient(cfg)

	// Create a request to select an object.
	request := &oss.SelectObjectRequest{
		Bucket: oss.Ptr(bucketName), // The bucket name.
		Key:    oss.Ptr(objectName), // The object name.
		SelectRequest: &oss.SelectRequest{
			Expression: oss.Ptr("select * from ossobject limit 10"), // Define an SQL expression to query the first 10 rows of data in the object.
			InputSerializationSelect: oss.InputSerializationSelect{
				JsonBodyInput: &oss.JSONSelectInput{
					JSONType: oss.Ptr("DOCUMENT"),
				},
			},
			OutputSerializationSelect: oss.OutputSerializationSelect{
				OutputHeader: oss.Ptr(true),
			},
		},
	}

	// Send the request to select the object.
	result, err := client.SelectObject(context.TODO(), request)
	if err != nil {
		log.Fatalf("failed to select object %v", err)
	}

	content, err := io.ReadAll(result.Body)
	if err != nil {
		log.Fatalf("failed to read object %v", err)
	}

	// Print the result of selecting the object.
	log.Printf("select object result:%#v\n", string(content))
}

References

• For the complete sample code for querying files, see GitHub sample.

• For more information about the API operation used to query files, see SelectObject.

• For more information about querying files, see Query files.