PolarDB:Download backup files

Release date

November 24, 2023

Scenarios

In addition to full data restoration and individual database or table restoration, PolarDB provides the backup download feature. You can download the backup files of a cluster to your computer for the following purposes:

• Query the data in a backup file.

• Query data at a specific point in time.

• Save backup files to your computer.

• Download backup files for auditing.

• Upload backup files to an Object Storage Service (OSS) bucket.

Billing

You are charged for file conversion and Internet traffic generated for the download.

Prerequisites

{
    "Version": "1",
    "Statement": [
        {
            "Effect": "Deny",
            "Action": "dbs:DescribeDownloadBackupSetStorageInfo",
            "Resource": "*"
        }
    ]
}

Limits

• The backup download feature allows you to export most schemas. However, some schemas cannot be exported.

  • You can export column information, primary key indexes, non-primary key indexes, unique indexes, partitioned table information, table engines, and table-level or database-level character sets and character collations.

  • You cannot export expression indexes, foreign keys, generated columns, hidden columns, views, functions, stored procedures, system variables, or triggers.

• The backup download feature does not support fields of spatial data types. If your PolarDB cluster contains fields of the following spatial data types, backup file conversion fails:

  GEOMETRY, POINT, LINESTRING, POLYGON, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON, and GEOMETRYCOLLECTION

• The CSV files that you export from your PolarDB cluster do not contain the following system databases:

  information_schema, mysql, performance_schema, sys, and __recycle_bin__

• If you set the Download Destination parameter to OSS, only Standard storage class is supported. For information about how to change storage classes, see Convert storage classes.

• You can download only the data of level-1 backup files. You cannot download the data of level-2 backup files.

• If cold data archiving is enabled for a cluster, you cannot download archived cold data. For more information, see Cold data archiving.

Procedure

1. Log on to the PolarDB console. Select a region in the upper-left corner and then click the ID of the cluster to go to the Basic Information page.

2. In the left-side navigation pane, click Backup and Restoration.

3. On the Backup and Restoration page, click Data Backups.

4. Find the backup set and click Download Cluster Backup in the Actions column.

   

   Note

   • By default, the PolarDB console displays the backup sets that are generated in the most recent eight days. If you want to view the backup sets that were generated more than eight days ago, you must change the default time range.

   • If Download Cluster Backup is not displayed, check whether the major engine version or region of the cluster meets the requirements that are described in Prerequisites.

5. In the Point in Time and Backup Set step of the wizard, select Download by Point in Time or Download by Backup Set and then click Next.

   

6. In the Instance, Database, and Table step of the wizard, click Next.

   Note

   By default, Instance Download is selected.

7. In the Destination and Format step of the wizard, configure the download destination and format.

   Important

   • We recommend that you set the Download Destination parameter to OSS to ensure efficiency.

   • The backup download task cannot be canceled after it is started.

   • OSS (recommended): PolarDB writes backup data directly to OSS. You must configure the bucket name and directory prefix of the OSS bucket.

     Note

     If you do not have the permissions to access OSS resources, follow the instructions in the console to click Authorize > Confirm Authorization Policy. After the permissions are granted, configure the parameters of the backup download task.

   • URL: PolarDB provides an internal or external URL. You can use the URL to download backup data.

     Note

     • If you set the Download Destination parameter to URL, the downloaded data is temporarily stored in the built-in storage of DBS. For more information, see Built-in storage and OSS.

     • URL downloads involve data packaging, which requires additional waiting time. The duration of this packaging process is largely dependent on the logical size of the backup set. If the logical size of the backup set is more than 1 TB, we recommend that you select OSS.

     

8. Configure the Download Format parameter.

   Note

   You can set the Download Format parameter to CSV, SQL, Parquet, or CSV-with-header.

9. Read and select the instructions, and then click Complete.

10. The Backup Download tab appears.

    Important

    • When you download backup files, you are charged file conversion fees and Internet traffic fees. For more information, see Billing rules.

    • If you use a third-party download tool to download backup files, additional traffic may be generated and you may be charged additional fees. Proceed with caution. For more information, see Download commands.

    • Computing resources are competed to convert the downloaded backup sets. As a result, temporary resource allocation may fail, and the download task fails. The download task may also fail due to unsupported special data formats. If your download task fails, try again or contact DBS technical support.

    • No fees are generated for failed tasks.

    • If you set the Download Destination parameter to OSS and the status of the task changes from Running to Finished, the download is successful. You can view and use the downloaded file in the specified OSS bucket.

      Note

      If you use this method, data is directly downloaded to your OSS bucket. You can use and delete the data based on your business requirements.

    • If you set the Download Destination parameter to URL and the status of the task changes to Finished, click Generate Link in the Download Destination column. In the Generate Link dialog box, configure the Validity Period parameter and click Generate Link. Then, you can download backup data by using the generated URL.

      Important

      • The validity period of the URL is from 5 minutes to one day. The default validity period is 2 hours.

      • We recommend that you save the URL at the earliest opportunity and keep the URL confidential.

      • You can obtain the download URL within three days after the download task is completed. After the URL expires, the downloaded data is deleted. If you want to use the data, you must initiate a new download task and obtain a new download URL.

FAQ

• How do I use the data backup files and log backup files that I downloaded?

  You can restore the data of the backup files that you downloaded to self-managed MySQL databases. For more information, see Restore the data of a PolarDB cluster to a self-managed MySQL database by using snapshot backup files.

• What do I do if the ERROR 1148 (42000): The used command is not allowed with this MySQL version error message appears when I restore the data of a backup file that I downloaded by using the backup download feature to a self-managed MySQL database?

  Execute the SHOW VARIABLES LIKE 'local_infile'; statement on the self-managed MySQL database. If OFF is returned in the output, execute the SET statement to set the global local_infile parameter to 1 to enable file import. After you perform the preceding operations, rerun the import script.

• Why is the backup file size displayed in the PolarDB console different from the size of the downloaded file?

  The downloaded backup file is compressed. As a result, the size of the downloaded backup file is smaller than the file size that is displayed in the PolarDB console. You can check the data integrity after the data is restored from the backup file.

• Can I directly restore a backup file that is downloaded from the PolarDB console to another PolarDB cluster?

  You cannot directly restore a backup file to another PolarDB cluster. If you want to restore the backup file to another PolarDB cluster, perform the following operations: Restore the backup file to a self-managed MySQL database and then migrate data from the self-managed database to the required PolarDB cluster. For more information, see Restore the data of a PolarDB cluster to a self-managed MySQL database by using snapshot backup files and Migrate data from a self-managed MySQL database to a PolarDB for MySQL cluster.

• Can I cancel an ongoing backup download task?

  No, you cannot cancel a backup download task after it is started.

Download commands

This section describes the commands that are commonly used to download backup files.

Command: nohup wget -c -t 0 "The URL of the backup file to download" -O The destination path and file name > The file to which the downloaded data is saved &
Example: nohup wget -c -t 0 "https://example.aliyundoc.com/examplebackup.qp.xb" -O /backup/examplebackup.qp.xb > /tmp/download.log &
The following section describes the options in the preceding command:
-t 0: enables an unlimited number of retries. 
-c: enables resumable uploads. 
-O: specifies the destination path and file name. 
nohup: prevents the download from being interrupted when you accidentally replicate data or disconnect your database client during the download. If you specify this option, the download process automatically exits after the download is completed.

Command: nohup curl -C - --retry 10 "The URL of the backup file to download" -o The user-defined name of the downloaded backup file > The file to which the downloaded data is saved &
Example: nohup curl -C --retry 10 "https://example.aliyundoc.com/examplebackup.qp.xb" -o backup.qp.xb > /tmp/download.log &
The following section describes the options in the preceding command:
--retry 10: enables up to 10 retries if the download fails. 
-C -: enables resumable uploads. 
-o: specifies the destination path and file name. 
nohup: prevents the download from being interrupted when you accidentally replicate data or disconnect your database client during the download. If you specify this option, the download process automatically exits after the download is completed.

Related API operations