ApsaraDB for OceanBase:Synchronize data from a MySQL tenant of OceanBase Database to an AnalyticDB for MySQL database

Background

• For the basic information about AnalyticDB for MySQL, see Basic data types.

• For information about table creation, partitioned tables, and distributed tables in AnalyticDB for MySQL, see CREATE TABLE.

Prerequisites

• The data transmission service has the privilege to access cloud resources. For more information, see Grant privileges to roles for data transmission.

• You have created a dedicated database user for data synchronization in the source OceanBase database and granted corresponding privileges to the user. For more information, see Create a database user.

Limitations

• The data transmission service supports AnalyticDB for MySQL V3.0.

• The data transmission service supports the synchronization of an object only when the following conditions are met: the database name, table name, and column name of the object are ASCII-encoded without special characters. The special characters are line breaks, spaces, and the following characters: . | " ' ` ( ) = ; / & \.

Considerations

• During incremental synchronization from OceanBase Database V4.x, if the STORED attribute is not marked for a generated column, the column value synchronized to the target is NULL. As a result, the data of this column received by the downstream system is not as expected.

• If the clocks between nodes or between the client and the server are out of synchronization, the latency may be inaccurate during incremental synchronization.

  For example, if the clock is earlier than the standard time, the latency can be negative. If the clock is later than the standard time, the latency can be positive.

• When you synchronize data from a MySQL tenant of OceanBase Database to an AnalyticDB for MySQL database, indexes are handled as follows:

  • When a table with a primary key is synchronized, delete all indexes except for the primary key index.

  • When a table without a primary key but with not-null unique indexes is synchronized, use the first not-null unique index as the primary key, and delete all other indexes.

  • Tables without primary keys or not-null unique indexes cannot be synchronized.

• If time of the TIMESTAMP type is used in the source or target and the time is within the range of Daylight Saving Time (DST), the data in the source and target may be inconsistent with a gap of 1 hour due to different time format processing methods used by the source and target.

  For example, if TIMEZONE is set to +8:00 for the source or target, the query results in the MySQL tenant of OceanBase Database are not in DST and those in AnalyticDB for MySQL are in DST. The data in AnalyticDB for MySQL is 1 hour ahead of that in the MySQL tenant of OceanBase Database.

• If you selected only Incremental Synchronization when you created a data synchronization task, the data transmission service requires that the local incremental logs in the source database be retained for at least 48 hours.

  If you selected Full Synchronization and Incremental Synchronization when you created a data synchronization task, the data transmission service requires that the local incremental logs in the source database be retained for at least seven days. Otherwise, the data synchronization task may fail or the data in the source and target databases may be inconsistent because the data transmission service cannot obtain incremental logs.

• If the source or target database contains table objects that differ only in letter cases, the data migration results may not be as expected due to case insensitivity in the source or target database.

Supported source and target instance types

In the following table, OB_MySQL stands for the MySQL tenant of OceanBase Database.

Data type mappings

Procedure

1. Log on to the ApsaraDB for OceanBase console and purchase a data synchronization task.

   For more information, see Purchase a data synchronization project.

2. Choose Data Transmission > Data Synchronization. On the page that appears, click Configuration for the data synchronization task.

   

   If you want to reference the configurations of an existing task, click Reference Configuration. For more information, see Reference and clear the configuration of a data synchronization task.

3. On the Select Source and Target page, configure the parameters.

   Parameter	Description
   Task Name	We recommend that you set it to a combination of digits and letters. It must not contain any spaces and cannot exceed 64 characters in length.
   Source	If you have created an OceanBase data source, select it from the drop-down list. Otherwise, click New Data Source in the drop-down list and create one in the dialog box that appears on the right. For more information about the parameters, see Create an OceanBase data source.
   Target	If you have created an AnalyticDB for MySQL data source, select it from the drop-down list. Otherwise, click New Data Source in the drop-down list and create one in the dialog box that appears on the right. For more information, see Create an ADB data source.
   Tag (Optional)	Select a target tag from the drop-down list. You can also click Manage Tags to create, modify, and delete tags. For more information, see Use tags to manage data synchronization projects.

4. Click Next. On the Select Synchronization Type page, specify the synchronization types for the current data synchronization task.

   

   The supported synchronization types are Schema Synchronization, Full Synchronization, and Incremental Synchronization. Options for Incremental Synchronization are DML Synchronization and DDL Synchronization. The supported DML operations are INSERT, DELETE, and UPDATE. You can select operations as needed. For more information, see Configure DDL/DML synchronization. For information about supported DDL operations, see Supported DDL operations for synchronization.

5. Click Next. On the Select Synchronization Objects page, select the objects to be synchronized in the current data synchronization task.

   You can use the Specify Objects or Match Rules option to specify synchronization objects. This topic describes how to specify synchronization objects by using the Specify Objects option. For information about how to configure matching rules, see the "Wildcard patterns for data migration/synchronization between databases" section in the Configure and modify matching rules topic.

   Important

   • The name of a table to be synchronized, as well as the names of columns in the table, must not contain Chinese characters.

   • If a database or table name contains a double dollar sign ($$), you cannot create the synchronization task.

   • If you selected DDL Synchronization in the Select Synchronization Type step, we recommend that you select synchronization objects by using the Match Rules option. This ensures that all new objects meeting the matching rules are synchronized. If you selected synchronization objects by using the Specify Objects option, new or renamed objects will not be synchronized.

   

   1. In the Select Synchronization Objects section, select Specify Objects.

   2. In the Select Synchronization Scope section, select the objects to be synchronized from the Source Object(s) list. You can select tables of one or more databases as the synchronization objects.

   3. Click > to add them to the Target Object(s) list.

   The data transmission service allows you to import objects by using text. It also allows you to rename objects, set row filters, and remove a single object or all objects.

   Note

   When you select Match Rules to specify synchronization objects, object renaming is implemented based on the syntax of the specified matching rules. In the operation area, you can only set filtering conditions and select sharding columns and the columns to be synchronized. For more information, see Configure and modify matching rules.

   Operation	Description
   Import objects	In the list on the right, click Import Objects in the upper-right corner. In the dialog box that appears, click OK. Important This operation will overwrite previous selections. Proceed with caution. In the Import Synchronization Objects dialog box, import the objects to be synchronized. You can import CSV files to rename databases or tables and set row filtering conditions. For more information, see Download and import the settings of synchronization objects. Click Validate. After you import the synchronization objects, check their validity. Column field mapping is not supported. After the validation succeeds, click OK.
   Rename objects	The data transmission service allows you to rename synchronization objects. For more information, see Rename a database table.
   Configure settings	You can use the WHERE clause to filter and select the columns to be synchronized and set the primary key columns, distribution keys, and partitioning keys. In the list on the right, hover over the object that you want to set. Click Settings. In the Settings dialog box, you can perform the following operations: Specify a standard SQL WHERE clause to filter data by row. For more information, see Use SQL conditions to filter data. Set the primary key column. By default, the primary key column of the current table is displayed. Multiple primary key columns are supported. You can delete the current primary key column and set the new primary key column by selecting the column from the drop-down list or searching for the column in the search box. Multiple primary key columns are supported. (Optional) Set distribution keys. Set partitioning keys. To set a partitioning key, perform the following operations: Enter an expression in the Partition Key Expression field, for example, PARTITION BY VALUE('id'). Set the table lifecycle, which is used to manage partitions. After the table lifecycle is set, partitions are sorted, and only the first N partitions are retained. Click OK.
   Remove one or all objects	The data transmission service allows you to remove a single or all synchronization objects that are added to the right-side list during data mapping. Remove a single synchronization object In the list on the right, hover over the object that you want to remove, and click Remove to remove the synchronization object. Remove all synchronization objects In the list on the right, click Remove All in the upper-right corner. In the dialog box that appears, click OK to remove all synchronization objects.

6. Click Next. On the Synchronization Options page, configure the parameters.

   • Full synchronization

     The following table describes the full synchronization parameters, which are displayed only if you have selected Full Synchronization on the Select Synchronization Type page.

     

     Parameter	Description
     Read Concurrency	The concurrency for reading data from the source during full synchronization. The maximum value is 512. A high concurrency may incur excessive stress on the source, thereby affecting the business.
     Write Concurrency	The concurrency for writing data to the target during full synchronization. The maximum value is 512. A high write concurrency may incur excessive stress on the target, affecting the business.
     Full Synchronization Rate Limit	You can choose whether to limit the full synchronization rate as needed. If you choose to limit the full synchronization rate, you must specify the records per second (RPS) and bytes per second (BPS). The RPS specifies the maximum number of data rows synchronized to the target per second during full synchronization, and the BPS specifies the maximum amount of data in bytes synchronized to the target per second during full synchronization. Note The RPS and BPS values specified here are only for throttling. The actual full synchronization performance is subject to factors such as the settings of the source and target and the instance specifications.
     Handle Non-empty Tables in Target Database	If you select Ignore, when the data to be inserted conflicts with existing data of a target table, the data transmission service logs the conflicting data while retaining the existing data. Important If you select Ignore, data is pulled in IN mode for full verification. In this case, verification is inapplicable if the target contains data that does not exist in the source, and the verification performance is downgraded. If you select Stop Migration and a target table contains records, an error prompting migration unsupported is reported during full migration. In this case, you must process the data in the target table before continuing with the migration. Important If you click Restore in the dialog box prompting the error, the data transmission service ignores this error and continues to migrate data. Proceed with caution.

   • Incremental synchronization

     The following table describes the incremental synchronization parameters, which are displayed only when you have selected Incremental Synchronization on the Select Synchronization Type page.

     

     Parameter	Description
     Write Concurrency	The concurrency for writing data to the target during incremental synchronization. The maximum value is 512. A high write concurrency may incur excessive stress on the target, affecting the business.
     Incremental Synchronization Rate Limit	You can choose whether to limit the incremental synchronization rate as needed. If you choose to limit the incremental synchronization rate, you must specify the requests per second (RPS) and bytes per second (BPS). The RPS specifies the maximum number of data rows synchronized to the target per second during incremental synchronization, and the BPS specifies the maximum amount of data in bytes synchronized to the target per second during incremental synchronization. Note The RPS and BPS values specified here are only for throttling. The actual incremental synchronization performance is subject to factors such as the settings of the source and target and the instance specifications.
     Incremental Synchronization Start Timestamp	This parameter is unavailable if you have selected Full Synchronization. If you have selected Incremental Synchronization but not Full Synchronization, specify a point in time after which data is to be synchronized. The default value is the current system time. For more information, see Set an incremental synchronization timestamp.

7. Click Precheck.

   During the precheck, the data transmission service detects the connection between the source and target. If an error is returned during the precheck, you can perform the following operations:

   • Identify and troubleshoot the problem and then perform the precheck again.

   • Click Skip in the Actions column of the failed precheck item. In the dialog box that prompts the consequences of the operation, click OK.

8. After the precheck succeeds, click Start Task.

   If you do not need to start the task now, click Save. You can manually start the task on the Synchronization Tasks page or by performing batch operations later. For more information about batch operations, see Perform batch operations on data synchronization projects.

   The data transmission service allows you to modify the synchronization objects when a synchronization task is running. For more information, see View and modify synchronization objects and their filter conditions. After the data synchronization task is started, it will be executed based on the selected synchronization types. For more information, see View details of a data synchronization task.

If the data synchronization task encounters an execution exception due to a network failure or slow startup of processes, you can click Restore on the Synchronization Tasks or Details page of the synchronization task.

References

• Create an OceanBase data source

• Create an ADB data source

• Perform batch operations on data synchronization projects

• View details of a data synchronization project