This topic describes how to synchronize data from an ApsaraDB RDS for PostgreSQL instance to an AnalyticDB for PostgreSQL instance by using Data Transmission Service (DTS). The data synchronization feature provided by DTS allows you to transfer and analyze data with ease.

Prerequisites

  • The tables to synchronize from the ApsaraDB RDS for PostgreSQL instance contain primary keys.
  • The destination AnalyticDB for PostgreSQL instance is created. For more information, see Create an instance.

Precautions

  • A single data synchronization task can synchronize data from only one database. To synchronize data from multiple databases, you must create a data synchronization task for each database.
  • During data synchronization, new tables that are created in the source database can also be synchronized. However, to ensure data consistency, you must execute the following statement on the new tables before they can be synchronized: 
    ALTER TABLE schema.table REPLICA IDENTITY FULL;
  • To ensure that the data synchronization task runs as expected, you can perform primary/secondary switchover only on an ApsaraDB RDS for PostgreSQL instance V11. In this case, you must set the rds_failover_slot_mode parameter to sync. For more information, see Logical Replication Slot Failover.
    Warning If you perform primary/secondary switchover on a self-managed PostgreSQL database or an ApsaraDB RDS for PostgreSQL instance of other versions, the data synchronization task stops.

Limits

  • Initial schema synchronization is not supported. DTS does not synchronize the schemas of the required objects from the source database to the destination database.
  • You can select only tables as the objects to synchronize.
  • DTS does not synchronize the following types of data: BIT, VARBIT, GEOMETRY, ARRAY, UUID, TSQUERY, TSVECTOR, and TXID_SNAPSHOT.
  • If you perform a DDL operation on an object to be synchronized in the source database during data synchronization, you must perform the operation in the destination database. Then, you must restart the data synchronization task.

SQL operations that can be synchronized

INSERT, UPDATE, and DELETE

Preparations

  1. Change the value of the wal_level parameter for the source RDS instance.
    Warning After you change the value of the wal_level parameter, you must restart the instance to apply the change. We recommend that you evaluate the impact on your business and change the parameter setting during off-peak hours.
    1. Log on to the ApsaraDB RDS console.
    2. In the top navigation bar, select the region where the RDS instance resides.
    3. Find the RDS instance and click its ID.
    4. In the left-side navigation pane, click Parameters.
    5. On the Parameters page, find the wal_level parameter and change the parameter value to logical.
  2. Create a database, schema, and table in the destination AnalyticDB for PostgreSQL instance based on the schema of the objects to synchronize. For more information, see SQL statements.

Procedure

  1. Purchase a data synchronization instance. For more information, see Purchase a DTS instance.
    Note On the buy page, set Source Instance to PostgreSQL, set Target Instance to AnalyticDB for PostgreSQL, and set Synchronization Topology to One-Way Synchronization.
  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 databases.
    Configure the source and destination databases
    Section Parameter Description
    N/A Synchronization Task Name DTS automatically generates a task name. We recommend that you specify an informative name to identify the task. You do not need to use a unique task name.
    Source Instance Details Instance Type Select RDS Instance.
    Instance Region The source region that you selected on the buy page. You cannot change the value of this parameter.
    The ID of the instance. Select the ID of the ApsaraDB RDS for PostgreSQL instance.
    Database Name Enter the name of the source database.
    Database Account Enter the account of the AnalyticDB for PostgreSQL instance, and the account must be a privileged account.
    Note If the source database runs on an ApsaraDB RDS for PostgreSQL instance V9.4 and you synchronize only DML operations, the database account must have the REPLICATION permission.
    Database Password Enter the password of the source 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 destination region that you selected on the buy page. You cannot change the value of this parameter.
    The ID of the instance. Select the ID of the AnalyticDB for PostgreSQL instance.
    Database Name Enter the name of the destination database.
    Note The database must exist in the AnalyticDB for PostgreSQL instance. Otherwise, you must create a database.
    Database Account Enter the initial account of the AnalyticDB for PostgreSQL instance. For more information, see Create a database account.
    Note You can also enter an account that has the RDS_SUPERUSER permission. For more information, see Manage users and permissions.
    Database Password Enter the password of the database account.
  7. In the lower-right corner of the page, click Set Whitelist and Next.
    Note DTS adds the CIDR blocks of DTS servers to the whitelists of the ApsaraDB RDS for PostgreSQ and AnalyticDB for PostgreSQL instances. This ensures that DTS servers can connect to the source and destination instances.
  8. Select the synchronization policy and the objects to synchronize.
    Select the objects to synchronize
    Section Parameter Description
    Specify Source and Destination Database Initial synchronization Initial Full Data Synchronization is selected by default. After the precheck, DTS synchronizes historical data of the required objects from the source instance to the destination instance. The data is 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 data to the existing data during initial full data synchronization. If you want to synchronize data from multiple tables to one table, you can select this mode.

    Synchronization Type

    Select the types of operations that you want to synchronize based on your business requirements.

    Note The Alter Table operation is not supported.
    • Insert
    • Update
    • Delete
    • AlterTable
    Select Object to be Synchronized None

    Select one or more tables from the Available section and click the Rightwards arrow icon to move the tables to the Selected section.

    Note
    • You can select only tables as the objects to synchronize.
    • You can use the object name mapping feature to rename the columns that are synchronized to the destination database. For more information, see Rename an object to be synchronized.
    Rename Databases and Tables None

    You can use the object name mapping feature to rename the objects that are synchronized to the destination instance. For more information, see Object name mapping.

    Retry Time for Failed Connections None
    By default, if DTS fails to connect to the source or destination database, DTS retries within the next 720 minutes (12 hours). You can specify the retry time based on your needs. If DTS reconnects to the source and destination databases within the specified time, DTS resumes the data synchronization task. Otherwise, the data synchronization task fails.
    Note When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time based on your business needs. You can also release the DTS instance at your earliest opportunity after the source and destination instances are released.
  9. In the lower-right corner of the page, click Precheck.
    Note
    • Before you can start the data synchronization task, DTS performs a precheck. You can start the data synchronization task only after the task passes the precheck.
    • If the task fails to pass the precheck, you can click the Info icon icon next to each failed item to view details.
      • You can troubleshoot the issues based on the causes and run a precheck again.
      • If you do not need to troubleshoot the issues, you can ignore failed items and run a precheck again.
  10. Close the Precheck dialog box after the following message is displayed: The precheck is passed. Then, the data synchronization task starts.
  11. Wait until the initial synchronization is complete and the data synchronization task is in the Synchronizing state.
    You can view the status of the data synchronization task on the Synchronization Tasks page. View the status of a data synchronization task