Synchronize data from an Apsara PolarDB for MySQL cluster to an AnalyticDB for PostgreSQL instance

Notes

• DTS uses read and write resources of the source and destination databases during initial full data synchronization. This may increase the database load. If the database performance is unfavorable, the specification is low, or the data volume is large, database services may become unavailable. For example, DTS occupies a large amount of read and write resources in the following cases: a large number of slow SQL queries are performed on the source database, the tables have no primary keys, or a deadlock occurs in the destination database. Before synchronizing data, you must evaluate the performance of the source and destination databases. We recommend that you synchronize data during off-peak hours. For example, you can synchronize data when the CPU usage of the source and destination databases is less than 30%.
• During initial full data synchronization, concurrent INSERT operations cause segments in the tables of the destination instance. After initial full data synchronization, the tablespace of the destination instance is larger than that of the source cluster.

Limits

• You can select only tables as the objects to be synchronized.
• You cannot synchronize the following types of data: BIT, VARBIT, GEOMETRY, ARRAY, UUID, TSQUERY, TSVECTOR, and TXID_SNAPSHOT.
• We recommend that you do not use gh-ost or pt-online-schema-change to perform DDL operations on objects during data synchronization. Otherwise, data synchronization may fail.

Supported SQL operations

• DML operations: INSERT, UPDATE, and DELETE
• DDL operations: ADD COLUMN, and RENAME COLUMN
  Note The CREATE TABLE operation is not supported. To synchronize data from a new table, you must add the table to the selected objects. For more information, see Add an object to a data synchronization task.

Supported synchronization topologies

• One-way one-to-one synchronization
• One-way one-to-many synchronization
• One-way many-to-one synchronization

Term mappings

Procedure

1. Purchase a data synchronization instance. For more information, see Purchase procedure.
   Note On the purchase page, select MySQL for the source instance and AnalyticDB for PostgreSQL for the destination instance. Select One-Way Synchronization as the synchronization topology.
2. Log on to the DTS console.
3. In the left-side navigation pane, click Data Synchronization.
4. At the top of the Synchronization Tasks page, select the region where the destination instance resides.
   
5. Find the data synchronization instance and click Configure Synchronization Channel in the Actions column.
6. Configure the source and destination instances.
   

   Section	Parameter	Description
   N/A	Synchronization Task Name	DTS automatically generates a task name. We recommend that you use an informative name for easy identification. You do not need to use a unique task name.
   Source Instance Details	Instance Type	Select User-Created Database Connected Over Express Connect, VPN Gateway, or Smart Access Gateway. Note You cannot select Apsara PolarDB for MySQL cluster as the instance type. To synchronize data from a Apsara PolarDB for MySQL cluster, you can select User-Created Database Connected Over Express Connect, VPN Gateway, or Smart Access Gateway.
   	Instance Region	The region of the Apsara PolarDB for MySQL cluster. The value is the same as that you selected when purchasing the data synchronization instance. You cannot change the value of this parameter.
   	Peer VPC	Select the ID of the VPC where the Apsara PolarDB for MySQL cluster resides. To obtain the VPC ID, you can log on to the Apsara PolarDB console and click the cluster ID. On the Overview page that appears, you can view the ID of the VPC where the cluster resides in the Basic Information section.
   	Database Type	The value of this parameter is set to MySQL and cannot be changed.
   	IP Address	Enter the private IP address of the Apsara PolarDB for MySQL cluster. In this example, enter 172.16.20.36. You can obtain the private IP address by pinging the VPC-facing endpoint of the Apsara PolarDB for MySQL cluster.
   	Port Number	Enter the port number of the Apsara PolarDB for MySQL cluster. The default port number is 3306.
   	Database Account	Enter the database account for the Apsara PolarDB for MySQL cluster. Note The account must have the REPLICATION SLAVE permission, the REPLICATION CLIENT permission, the SHOW VIEW permission, and the permission to perform SELECT operations on the required objects.
   	Database Password	Enter the password for the database account.
   Destination Instance Details	Instance Type	The value of this parameter is set to AnalyticDB for PostgreSQL and cannot be changed.
   	Instance Region	The region of the destination instance. The value is the same as that you selected when purchasing the data synchronization instance. You cannot change the value of this parameter.
   	Instance ID	Select the ID of the destination AnalyticDB for PostgreSQL instance.
   	Database Name	Enter the name of the destination database in the AnalyticDB for PostgreSQL instance.
   	Database Account	Enter the database account for the destination AnalyticDB for PostgreSQL instance. Note The database account must have the ALL permission for the objects to be synchronized.
   	Database Password	Enter the password for the database account.

7. In the lower-right corner of the page, click Set Whitelist and Next.
   Note The CIDR blocks of DTS servers are automatically added to the whitelists of the Apsara PolarDB for MySQL cluster and the AnalyticDB for PostgreSQL instance. This ensures that DTS servers can connect to the source cluster and destination instance.
8. Configure the synchronization policy and objects.
   

   Section	Parameter	Description
   Synchronization policy	Initial Synchronization	You must select both Initial Schema Synchronization and Initial Full Data Synchronization in most cases. After the precheck, DTS synchronizes the schemas and data of the required objects from the source instance to the destination instance. The schemas and data are the basis for subsequent incremental synchronization.
   	Processing Mode In Existed Target Table	Clear Target Table Skips the Schema Name Conflict item during the precheck. Clears the data in the destination table before initial full data synchronization. If you want to synchronize your business data after testing the data synchronization task, you can select this mode. Ignore Skips the Schema Name Conflict item during the precheck. Adds new data to the existing data during initial full data synchronization. You can select this mode if you want to synchronize data from multiple tables to one table.
   	Synchronization Type	Select the types of operations that you want to synchronize based on your business requirements. Insert Update Delete Alter Table
   Objects to be synchronized	N/A	Select tables from the Available section and click the right arrow () icon to add the tables to the Selected section. Note You can select only tables as the objects to be synchronized. You can change the names of columns in the destination database by using the object name mapping feature provided by DTS. For more information about how to use this feature, see Specify the name of an object in the destination instance.

9. Specify the primary key column and distribution column of the table that you want to synchronize to the AnalyticDB for PostgreSQL instance.
   

   Note The page in this step appears only if you select Initial Schema Synchronization.
10. In the lower-right corner of the page, click Precheck.
    Note

    • Before you can start the data synchronization task, a precheck is performed. You can start the data synchronization task only after the task passes the precheck.
    • If the task fails to pass the precheck, click the icon next to each failed item to view details. Troubleshoot the issues based on the causes and run the precheck again.
11. Close the Precheck dialog box after the following message is displayed: The precheck is passed. Then, the data synchronization task starts.
12. Wait until the initial synchronization is complete and the data synchronization task is in the Synchronizing state.
    On the Synchronization Tasks page, view the status of the data synchronization task.