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    Data Transmission Service:Migrate data from an ApsaraDB RDS for MySQL instance to an ApsaraDB for ClickHouse cluster

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    Data Transmission Service:Migrate data from an ApsaraDB RDS for MySQL instance to an ApsaraDB for ClickHouse cluster

    Last Updated:Sep 11, 2025

    You can use Data Transmission Service (DTS) to migrate data from a MySQL database, such as a self-managed MySQL database or an ApsaraDB RDS for MySQL instance, to an ApsaraDB for ClickHouse cluster. This lets you easily transfer data for centralized analysis. This topic uses an ApsaraDB RDS for MySQL instance as an example to demonstrate how to configure a data migration from ApsaraDB RDS for MySQL to an ApsaraDB for ClickHouse cluster.

    Prerequisites

    A destination ApsaraDB for ClickHouse cluster that runs version 20.8 or later is created. For more information, see Create a cluster.

    Note

    The storage space of the destination ApsaraDB for ClickHouse cluster must be larger than the storage space used by the source ApsaraDB RDS for MySQL instance.

    Usage notes

    Type

    Description

    Source database restrictions

    • If you migrate objects at the table level and need to edit them, such as using the object name mapping feature, a single data migration task supports a maximum of 1,000 tables. If you exceed this limit, a request error is reported after you submit the task. In this case, split the tables to migrate into multiple tasks or configure a task to migrate the entire database.

    • If you want to migrate incremental data, the following requirements for binary logs must be met:

      • The binary logging feature is enabled. The binlog_format parameter is set to row and the binlog_row_image parameter is set to full. Otherwise, error messages are returned during the precheck and the data migration task fails to be started.

        Important

        If the source database is a self-managed MySQL database deployed in a dual-primary cluster, you must set the log_slave_updates parameter to ON. This ensures that DTS can obtain all binary logs.

      • The binary logs of an ApsaraDB RDS for MySQL instance must be stored for at least three days. We recommend that you store the binary logs seven days. The binary logs of a self-managed MySQL database must be stored for at least seven days. Otherwise, DTS may fail to obtain the binary logs and the task may fail. In exceptional circumstances, data inconsistency or loss may occur. Make sure that you configure the retention period of binary logs based on the preceding requirements. Otherwise, the service reliability or performance stated in the Service Level Agreement (SLA) of DTS may not be guaranteed.

        Note

        For more information about how to set Retention Period of the binary logs of an ApsaraDB RDS for MySQL instance, see Configure parameters based on which the system automatically deletes the binary log files of an RDS instance.

    • In incremental data migration, an ApsaraDB RDS for MySQL instance that does not record transaction logs, such as a read-only ApsaraDB RDS for MySQL V5.6 instance, cannot be used as the source database.

    • Limits on operations to be performed on the source database:

      • During schema migration and full data migration, do not execute DDL statements to change the schemas of databases or tables. Otherwise, the data migration task fails.

      • If you perform only full data migration, do not write data to the source database during data migration. Otherwise, data inconsistency between the source and destination databases occurs. To ensure data consistency, we recommend that you select schema migration, full data migration, and incremental data migration as the migration types.

    • The data generated by change operation of binary logs, such as data restored from a physical backup or data from a cascade operation, is not recorded and migrated to the destination database when the data migration instance is running.

      Note

      If the change data is not recorded and migrated to the destination database, you can migrate full data again on the premise that your business is not affected.

    • If the source database is MySQL database 8.0.23 or later, and the data to be migrated includes invisible columns, the data of the columns cannot be obtained and data loss occurs.

      Note

      • To make the columns visible, run the ALTER TABLE <table_name> ALTER COLUMN <column_name> SET VISIBLE; command. For more information, see Invisible Columns.

      • Tables that do not have primary keys automatically generate invisible primary keys. You need to make the invisible primary keys visible. For more information, see Generated Invisible Primary Keys.

    Other restrictions

    • If the DDL statements in the source ApsaraDB RDS for MySQL instance do not follow standard MySQL syntax, the migration task may fail or data may be lost.

    • Migration of INDEX, PARTITION, VIEW, PROCEDURE, FUNCTION, TRIGGER, and FK is not supported.

    • The RENAME TABLE operation cannot be migrated.

    • If the source database has online DDL change operations in temporary table mode, such as multi-table merge scenarios, it may cause data loss in the destination database or failure of the migration instance.

    • When you perform online DDL changes on the source using DMS or the gh-ost tool, DTS migrates only the original DDL statement to the destination. In this scenario, DTS does not need to migrate large amounts of temporary table data, but it may cause locked tables in the destination.

      Note

      Migration of online DDL changes performed using tools such as pt-online-schema-change on the source is not supported. If such changes exist on the source, it may cause data loss in the destination or failure of the migration instance.

    • The time-type data in ApsaraDB for ClickHouse has range limitations. If the time data in ApsaraDB RDS for MySQL is outside this range, the time migrated to ApsaraDB for ClickHouse will be incorrect. For information about the range limitations, see Time information.

    • You cannot select nullable fields for the Partition Key. Otherwise, the migration task fails.

      Note

      The partition key supports only fields of the BIGINT, INT, TIMESTAMP, DATETIME, and DATE types.

    • The number of databases to migrate must not exceed the ApsaraDB for ClickHouse limit of 256.

    • The names of the databases, tables, and columns to migrate must comply with the ApsaraDB for ClickHouse naming conventions. For more information, see Object naming conventions.

    • During schema migration, DTS adds the _sign, _is_deleted, and _version fields to the destination tables. If you do not select Schema Migration when you configure Migration Types, you must manually create the tables to receive data in the destination and add these extra fields. For information about table creation requirements and field details, see Table and field information.

    • Before migrating data, evaluate the performance of the source and destination databases. We recommend that you perform data migration during off-peak hours. Otherwise, initial full data synchronization consumes read and write resources of the source and destination databases, which may increase the database load.

    • If you migrate one or more tables instead of an entire database, do not use tools such as pt-online-schema-change to perform online DDL operations on the migration objects in the source database. Otherwise, the migration fails.

      You can use Data Management (DMS) to perform online DDL operations. For more information, see Perform lock-free schema changes.

    • During DTS migration, do not allow data from sources other than DTS to be written to the destination database. Otherwise, data inconsistency between the source and destination databases occurs.

    • If the source database is an ApsaraDB RDS for MySQL instance for which the EncDB feature is enabled, full data migration cannot be performed.

      Note

      ApsaraDB RDS for MySQL instances that have the Transparent Data Encryption (TDE) feature enabled support schema migration, full data migration, and incremental data migration.

    • If a DTS task fails to run, DTS technical support will try to restore the task within 8 hours. During the restoration, the task may be restarted, and the parameters of the task may be modified.

      Note

      Only the parameters of the DTS task may be modified. The parameters of databases are not modified. The parameters that may be modified include but are not limited to the parameters in the "Modify instance parameters" section of the Modify the parameters of a DTS instance topic.

    Special cases

    • If the source database is a self-managed MySQL database, take note of the following limits:

      • If you perform a primary/secondary switchover on the source database when the data migration task is running, the task fails.

      • DTS calculates migration latency based on the timestamp of the latest migrated data in the destination database and the current timestamp in the source database. If no DML operation is performed on the source database for a long time, the migration latency may be inaccurate. If the latency of the data migration task is excessively high, you can perform a DML operation on the source database to update the latency.

        Note

        If you select an entire database as the object to be migrated, you can create a heartbeat table. The heartbeat table is updated or receives data every second.

      • DTS executes the CREATE DATABASE IF NOT EXISTS `test` statement in the source database as scheduled to move forward the binary log file position.

    • If the source database is an Apsara RDS for MySQL instance, take note of the following limit:

      • In incremental data migration, an ApsaraDB RDS for MySQL instance that does not record transaction logs, such as a read-only ApsaraDB RDS for MySQL V5.6 instance, cannot be used as the source database.

      • DTS executes the CREATE DATABASE IF NOT EXISTS `test` statement in the source database as scheduled to move forward the binary log file position.

    Billing

    Migration type

    Configuration fees for links

    Data transfer cost

    Schema migration and full data migration

    Free of charge.

    This example does not incur this cost.

    Incremental data migration

    Charged. For more information, see Billing overview.

    SQL operations that support incremental migration

    Operation type

    SQL operation

    DML

    INSERT, UPDATE, DELETE

    DDL

    • CREATE TABLE, DROP TABLE, TRUNCATE TABLE

    • ADD COLUMN, MODIFY COLUMN, DROP COLUMN

    Data type mappings

    The data types supported by MySQL and ClickHouse do not have a one-to-one mapping. Therefore, during initial schema synchronization, DTS maps the data types from the source database to compatible data types in the destination database. For more information, see Data type mappings between heterogeneous databases.

    Permissions required for database accounts

    Database

    Required permissions

    How to create and grant permissions

    Source ApsaraDB RDS for MySQL

    Read permissions on the objects that you want to migrate.

    Create an account and Modify account permissions.

    Destination ApsaraDB for ClickHouse cluster

    • For version 22.8 or later, you need read and write permissions on the destination database. A privileged account meets these requirements.

    • Version 21.8: Read, Write and Set Permissions and Allow DDL.

    Manage accounts for a Community-compatible Edition cluster

    Note

    If you do not use the ApsaraDB RDS for MySQL console to create the source database account and grant permissions, make sure that the account has the REPLICATION CLIENT, REPLICATION SLAVE, SHOW VIEW, and SELECT permissions.

    Procedure

    1. Use one of the following methods to go to the Data Migration page and select the region in which the data migration instance resides.

      DTS console

      1. Log on to the DTS console.

      2. In the left-side navigation pane, click Data Migration.

      3. In the upper-left corner of the page, select the region in which the data migration instance resides.

      DMS console

      Note

      The actual operation may vary based on the mode and layout of the DMS console. For more information, see Simple mode and Customize the layout and style of the DMS console.

      1. Log on to the DMS console.

      2. In the top navigation bar, move the pointer over Data + AI > DTS (DTS) > Data Migration.

      3. From the drop-down list to the right of Data Migration Tasks, select the region in which the data synchronization instance resides.

    2. Click Create Task to go to the task configuration page.

    3. Configure the source and destination databases. The following table describes the parameters.

      Category

      Configuration

      Description

      None

      Task Name

      The name of the DTS task. DTS automatically generates a task name. We recommend that you specify a descriptive name that makes it easy to identify the task. You do not need to specify a unique task name.

      Source Database

      Select Existing Connection

      • If you use a database instance that is registered with DTS, select the instance from the drop-down list. DTS automatically populates the following database parameters for the instance. For more information, see Manage database connections.

        Note

        In the DMS console, you can select the database instance from the Select a DMS database instance drop-down list.

      • If you fail to register the instance with DTS, or you do not need to use the instance that is registered with DTS, you must configure the following database information.

      Database Type

      Select MySQL.

      Access Method

      Select Alibaba Cloud Instance.

      Instance Region

      Select the region where the source ApsaraDB RDS for MySQL instance resides.

      Replicate Data Across Alibaba Cloud Accounts

      This example describes migration within the same Alibaba Cloud account. Select No.

      RDS Instance ID

      Select the ID of the source ApsaraDB RDS for MySQL instance.

      Database Account

      Enter the database account for the source ApsaraDB RDS for MySQL instance. For information about the required permissions, see Permissions required for database accounts.

      Database Password

      The password that is used to access the database.

      Encryption

      Specifies whether to encrypt the connection to the database. You can select Non-encrypted or SSL-encrypted based on your business requirements. If you want to set this parameter to SSL-encrypted, you must enable SSL encryption for the ApsaraDB RDS for MySQL instance before you configure the DTS task. For more information, see Use a cloud certificate to enable SSL encryption.

      Destination Database

      Select Existing Connection

      • If you use a database instance that is registered with DTS, select the instance from the drop-down list. DTS automatically populates the following database parameters for the instance. For more information, see Manage database connections.

        Note

        In the DMS console, you can select the database instance from the Select a DMS database instance drop-down list.

      • If you fail to register the instance with DTS, or you do not need to use the instance that is registered with DTS, you must configure the following database information.

      Database Type

      Select ClickHouse.

      Access Method

      Select Alibaba Cloud Instance.

      Instance Region

      Select the region where the destination ApsaraDB for ClickHouse cluster resides.

      Replicate Data Across Alibaba Cloud Accounts

      This example describes migration within the same Alibaba Cloud account. Select No.

      Cluster Type

      Select the type of the ApsaraDB for ClickHouse cluster as needed.

      Cluster ID

      Select the ID of the destination ApsaraDB for ClickHouse cluster.

      Database Account

      Enter the database account for the destination ApsaraDB for ClickHouse cluster. For information about the required permissions, see Permissions required for database accounts.

      Database Password

      The password that is used to access the database.

    4. In the lower part of the page, click Test Connectivity and Proceed.

      Note

      • Make sure that the CIDR blocks of DTS servers can be automatically or manually added to the security settings of the source and destination databases to allow access from DTS servers. For more information, see Add the CIDR blocks of DTS servers.

      • If the source or destination database is a self-managed database and its Access Method is not set to Alibaba Cloud Instance, click Test Connectivity in the CIDR Blocks of DTS Servers dialog box.

    5. Configure the objects to be migrated.

      1. On the Configure Objects page, configure the objects that you want to migrate.

        Configuration

        Description

        Migration Types

        • To perform only full data migration, select Schema Migration and Full Data Migration.

        • To ensure service continuity during data migration, select Schema Migration, Full Data Migration, and Incremental Data Migration.

        Note

        • If you do not select Schema Migration, make sure a database and a table are created in the destination database to receive data and the object name mapping feature is enabled in Selected Objects.

        • If you do not select Incremental Data Migration, we recommend that you do not write data to the source database during data migration. This ensures data consistency between the source and destination databases.

        Processing Mode of Conflicting Tables

        • Precheck and Report Errors: checks whether the destination database contains tables that use the same names as tables in the source database. If the source and destination databases do not contain tables that have identical table names, the precheck is passed. Otherwise, an error is returned during the precheck and the data migration task cannot be started.

          Note

          If the source and destination databases contain tables with identical names and the tables in the destination database cannot be deleted or renamed, you can use the object name mapping feature to rename the tables that are migrated to the destination database. For more information, see Map object names.

        • Ignore Errors and Proceed: skips the precheck for identical table names in the source and destination databases.

          Warning

          If you select Ignore Errors and Proceed, data inconsistency may occur and your business may be exposed to the following potential risks:

          • If the source and destination databases have the same schema, and a data record has the same primary key as an existing data record in the destination database, the following scenarios may occur:

            • During full data migration, DTS does not migrate the data record to the destination database. The existing data record in the destination database is retained.

            • During incremental data migration, DTS migrates the data record to the destination database. The existing data record in the destination database is overwritten.

          • If the source and destination databases have different schemas, only specific columns are migrated or the data migration task fails. Proceed with caution.

        Capitalization of Object Names in Destination Instance

        The capitalization of database names, table names, and column names in the destination instance. By default, DTS default policy is selected. You can select other options to make sure that the capitalization of object names is consistent with that of the source or destination database. For more information, see Specify the capitalization of object names in the destination instance.

        Source Objects

        Select one or more objects from the Source Objects section. Click the 向右小箭头 icon to add the objects to the Selected Objects section.

        Note

        You can select objects at the database or table level.

        Selected Objects

        • To rename an object that you want to migrate to the destination instance, right-click the object in the Selected Objects section. For more information, see Map the name of a single object.

        • To rename multiple objects at a time, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time.

        Note

        • To set filter conditions for data, right-click the table to be migrated in the Selected Objects box and set the filter conditions in the dialog box that appears. For more information, see Set filter conditions.

        • If you use the object name mapping feature, other objects that depend on the renamed object may fail to migrate.

      2. Click Next: Advanced Settings to configure advanced settings.

        Configuration

        Description

        Dedicated Cluster for Task Scheduling

        By default, DTS schedules the data migration task to the shared cluster if you do not specify a dedicated cluster. If you want to improve the stability of data migration tasks, purchase a dedicated cluster. For more information, see What is a DTS dedicated cluster.

        Time zone of destination database

        You can select the time zone for DateTime data that is written to the ApsaraDB for ClickHouse cluster.

        Retry Time for Failed Connections

        The retry time range for failed connections. If the source or destination database fails to be connected after the data migration task is started, DTS immediately retries a connection within the retry time range. Valid values: 10 to 1,440. Unit: minutes. Default value: 720. We recommend that you set the parameter to a value greater than 30. If DTS is reconnected to the source and destination databases within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails.

        Note

        • If you specify different retry time ranges for multiple data migration tasks that share the same source or destination database, the value that is specified later takes precedence.

        • When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time range based on your business requirements. You can also release the DTS instance at the earliest opportunity after the source database and destination instance are released.

        Retry Time for Other Issues

        The retry time range for other issues. For example, if DDL or DML operations fail to be performed after the data migration task is started, DTS immediately retries the operations within the retry time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set the parameter to a value greater than 10. If the failed operations are successfully performed within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails.

        Important

        The value of the Retry Time for Other Issues parameter must be smaller than the value of the Retry Time for Failed Connections parameter.

        Enable Throttling for Full Data Migration

        Specifies whether to enable throttling for full data migration. During full data migration, DTS uses the read and write resources of the source and destination databases. This may increase the loads of the database servers. You can enable throttling for full data migration based on your business requirements. To configure throttling, you must configure the Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) parameters. This reduces the loads of the destination database server.

        Note

        You can configure this parameter only if you select Full Data Migration for the Migration Types parameter.

        Enable Throttling for Incremental Data Migration

        Specifies whether to enable throttling for incremental data migration. To configure throttling, you must configure the RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) parameters. This reduces the loads of the destination database server.

        Note

        You can configure this parameter only if you select Incremental Data Migration for the Migration Types parameter.

        Whether to delete SQL operations on heartbeat tables of forward and reverse tasks

        Specifies whether to write SQL operations on heartbeat tables to the source database while the DTS instance is running. Valid values:

        • Yes: does not write SQL operations on heartbeat tables. In this case, a latency of the DTS instance may be displayed.

        • No: writes SQL operations on heartbeat tables. In this case, features such as physical backup and cloning of the source database may be affected.

        Environment Tag

        You can select an environment tag to identify the instance. In this example, you do not need to select a tag.

        Configure ETL

        Specifies whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values:

        Monitoring and Alerting

        Specifies whether to configure alerting for the data migration task. If the task fails or the migration latency exceeds the specified threshold, the alert contacts receive notifications. Valid values:

      3. Click Next: Configure Database and Table Fields to configure the Type, Primary Key Column, Sort Key, Distribution Key, and Partition Key for the destination table in ClickHouse.

        • DTS provides a default configuration. To modify this configuration, you can set Definition Status to All.

        • The Primary Key Column and Sort Key can be composite keys. You can select multiple fields from the corresponding drop-down lists for the Primary Key Column or Sort Key. You must select one or more columns from the Primary Key Column to serve as the Partition Key. You can select only one field for the Distribution Key. For more information about primary keys, sort keys, and partition keys, see CREATE TABLE.

          Note

          • You can leave the Partition Key unconfigured, but you cannot select a nullable field for it because this will cause the migration task to fail.

          • The partition key supports only fields of the BIGINT, INT, TIMESTAMP, DATETIME, and DATE data types. For more information about its calculation logic, see Calculation logic for partition keys.

    6. Save the task settings and run a precheck.

      • To view the parameters to be specified when you call the relevant API operation to configure the DTS task, move the pointer over Next: Save Task Settings and Precheck and click Preview OpenAPI parameters.

      • If you do not need to view or have viewed the parameters, click Next: Save Task Settings and Precheck in the lower part of the page.

      Note

      • Before you can start the data migration task, DTS performs a precheck. You can start the data migration task only after the task passes the precheck.

      • If the task fails to pass the precheck, click View Details next to each failed item. After you analyze the causes based on the check results, troubleshoot the issues. Then, run a precheck again.

      • If an alert is triggered for an item during the precheck:

        • If an alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issues. Then, run a precheck again.

        • If the alert item can be ignored, click Confirm Alert Details. In the View Details dialog box, click Ignore. In the message that appears, click OK. Then, click Precheck Again to run a precheck again. If you ignore the alert item, data inconsistency may occur, and your business may be exposed to potential risks.

    7. Purchase the instance.

      1. Wait until Success Rate becomes 100%. Then, click Next: Purchase Instance.

      2. On the Purchase Instance page, configure the Instance Class parameter for the data migration instance. The following table describes the parameters.

        Section

        Parameter

        Description

        New Instance Class

        Resource Group

        The resource group to which the data migration instance belongs. Default value: default resource group. For more information, see What is Resource Management?

        Instance Class

        DTS provides instance classes that vary in the migration speed. You can select an instance class based on your business scenario. For more information, see Instance classes of data migration instances.

      3. Read and agree to Data Transmission Service (Pay-as-you-go) Service Terms by selecting the check box.

      4. Click Buy and Start. In the message that appears, click OK.

        You can view the progress of the task on the Data Migration page.

        Note

        • If a data migration task cannot be used to migrate incremental data, the task automatically stops. The Completed is displayed in the Status section.

        • If a data migration task can be used to migrate incremental data, the task does not automatically stop. The incremental data migration task never stops or completes. The Running is displayed in the Status section.

    Appendix

    Time information

    Data type

    Minimum value

    Maximum value

    Date

    1970-01-01 00:00:00

    2149-06-06 00:00:00

    Date32

    1925-01-01 00:00:00

    2283-11-11 00:00:00

    DateTime

    1970-01-01 08:00:00

    2106-02-07 14:28:15

    DateTime64

    1925-01-01 08:00:00

    2283-11-12 07:59:59

    Table and field information

    Table information

    If you do not use the object name mapping feature, the tables you create must meet the following requirements.

    Important

    If the destination table includes an ENGINE, it must be ENGINE = ReplicatedReplacingMergeTree(_version, _is_deleted). Otherwise, data inconsistency may occur.

    • ClickHouse Community Edition instance: You need to create one local table and one distributed table. The name of the distributed table must be the same as the source table name. The name of the local table must be <distributed_table_name>_local.

    • ClickHouse Enterprise Edition instance: You need to create a table with the same name as the source table.

    Field information

    Note

    In a ClickHouse instance, you can run the select * from table_name final where _sign>0; statement to query data. The where condition filters out deleted data, and the final keyword after the table name filters out data with the same sort key.

    Version

    Name

    Data type

    Default value

    Description

    Community Edition earlier than 23.8

    _sign

    Int8

    1

    The type of DML operation.

    • INSERT: The record is 1.

    • UPDATE: The record is 1.

    • DELETE: The record is -1.

    _version

    UInt64

    1

    The timestamp when the data was written to ClickHouse.

    Enterprise Edition and Community Edition 23.8 and later

    _sign

    Int8

    1

    The type of DML operation.

    • INSERT: The record is 1.

    • UPDATE: The record is 1.

    • DELETE: The record is -1.

    _is_deleted

    UInt8

    0

    Indicates whether the record is deleted:

    • Insert: The record is 0.

    • Delete: The record is 1.

    • Update: The record is 0.

    _version

    UInt64

    1

    The timestamp when the data was written to ClickHouse.

    Calculation logic for partition keys

    Source field type

    Partition key calculation logic

    BIGINT

    intDiv(" + tablePartKey + ", 18014398509481984)

    INT

    intDiv(" + tablePartKey + ", 4194304)

    TIMESTAMP

    toYYYYMM(" + tablePartKey + ")

    DATETIME

    DATE