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    Data Transmission Service:Synchronize PolarDB-X 2.0 to Elasticsearch

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    Data Transmission Service:Synchronize PolarDB-X 2.0 to Elasticsearch

    Last Updated:Jun 26, 2026

    This topic describes how to use DTS to synchronize data from a PolarDB-X 2.0 instance to an Elasticsearch instance.

    Prerequisites

    • You have a source PolarDB-X 2.0 instance.

    • You have a destination Elasticsearch cluster. For more information, see Create an Alibaba Cloud Elasticsearch instance.

    • For a list of supported versions for the source and destination, see Synchronization solution overview.

    • The available storage space in the destination Elasticsearch cluster must be greater than the data size of the source PolarDB-X 2.0 instance.

    Limitations

    Note

    • During schema synchronization, DTS synchronizes foreign keys from the source database to the destination database.

    • During full data synchronization and incremental data synchronization, DTS temporarily disables the constraint check and cascade operations on foreign keys at the session level. If cascading updates or deletions occur in the source database during synchronization, data inconsistencies may occur.

    Type

    Description

    Source database limitations

    • Synchronized tables must have a primary key or a unique constraint. Otherwise, duplicate data may occur in the destination database.

    • DTS does not support Enterprise Edition PolarDB-X 2.0 read-only instances as the source database.

    • If you synchronize tables individually and perform edits, such as column name mapping, a single data synchronization task supports a maximum of 5,000 tables. To synchronize more than 5,000 tables, split them across multiple tasks or configure the task to synchronize the entire database. Otherwise, a request error may occur after you submit the task.

    • Binary log requirements:

      • You must enable the binary log feature in the PolarDB-X 2.0 console and set the binlog_row_image parameter to full. For more information, see Parameter settings. Otherwise, the precheck fails and the data synchronization task cannot start.

      • For incremental data synchronization, you must retain the source database's binary logs for over 24 hours. For tasks that combine full and incremental synchronization, the retention period must be at least 7 days. After the full data synchronization is complete, you can reduce the retention period to 24 hours. The DTS SLA does not cover issues caused by an insufficient binary log retention period.

    • If a table name in the source PolarDB-X 2.0 instance contains uppercase letters, DTS supports only schema synchronization for that table.

    • DTS does not support synchronizing table groups (TABLEGROUP) or databases and tables that have the Locality attribute.

    • DTS does not support synchronizing tables whose names are reserved keywords, such as select.

    • DTS cannot synchronize partitions of databases in DRDS mode on a PolarDB-X 2.0 instance.

    • Do not run DDL operations that change database or table schemas during schema synchronization or full synchronization. Otherwise, the synchronization task fails.

      Note

      During full synchronization, DTS queries the source database. This creates metadata locks that may block DDL operations on the source database.

    • During the operation of a DTS synchronization task, changing the type of a broadcast table in the source PolarDB-X 2.0 instance (for example, changing a broadcast table to a regular table or a sharded table) is not supported. To change the table type, stop the synchronization task first, and then reconfigure the synchronization task after the change is complete.

    Other limitations

    • DTS does not synchronize DDL operations. If you perform a DDL operation on a source table during synchronization, you must remove the sync object, remove the corresponding index from the Elasticsearch instance, and then add the sync object again. For more information, see Remove a sync object and Add a sync object.

    • To add a column to a source table, modify the mappings of the corresponding index in the Elasticsearch instance, perform the DDL operation on the source database, and then pause and restart the data synchronization task.

    • You cannot synchronize data to Elasticsearch indexes that contain parent-child relationships or Join field types. Doing so may cause task errors or query failures in the destination.

    • Evaluate the performance of your source and destination databases before starting data synchronization. Perform the synchronization during off-peak hours, as initial full data synchronization consumes significant resources and increases the database load.

    • Initial full data synchronization runs concurrent INSERT operations, which can cause table fragmentation in the destination database. Consequently, the destination instance may occupy more tablespace than the source instance after synchronization.

    • Do not use tools like pt-online-schema-change to perform online DDL operations on the objects being synchronized in the source database. Otherwise, the synchronization task fails.

    • During DTS synchronization, do not write data to the destination database from any source other than DTS. This can cause data inconsistency between the source and destination databases. For example, if you use DMS to perform an online DDL change while data is being written from another source, data loss may occur in the destination database.

    • Development and test specifications of Elasticsearch instances are not supported.

    • If a task fails, DTS support staff will attempt to restore it within eight hours. During restoration, they may restart the task or adjust its parameters.

      Note

      Only DTS task parameters are modified—not database parameters. Parameters that may be adjusted include those listed in Modify instance parameters.

    Other precautions

    DTS periodically updates the dts_health_check.ha_health_check table in the source database to advance the binary log file position.

    Billing

    Synchronization type

    Pricing

    Schema synchronization and full data synchronization

    Free of charge.

    Incremental data synchronization

    Charged. For more information, see Billing overview.

    Synchronization topologies

    • One-way one-to-one synchronization

    • One-way one-to-many synchronization

    • One-way many-to-one synchronization

    For more information, see Synchronization topologies.

    Supported SQL operations

    Operation type

    SQL statement

    DML

    INSERT, UPDATE, and DELETE

    Note

    Column removal using UPDATE is not synchronized.

    Data type mapping

    • A source database and an Elasticsearch instance support different data types that cannot always be mapped directly. During structure initialization, DTS maps data types based on those supported by the target Elasticsearch instance. For more information, see Data type mapping for structure initialization.

      Note

      During the DTS schema migration process, DTS does not set the dynamic parameter in mapping. The behavior of this parameter depends on the settings of your Elasticsearch instance. If your source data is of the JSON type, you must ensure that for a specific key, its corresponding values have the same data type across all rows in a table. Otherwise, DTS may encounter synchronization issues. For more information, see dynamic.

    • The mapping between Elasticsearch and a relational database varies by Elasticsearch version.

      Important

      Starting with Elasticsearch 7.0, an index no longer supports multiple types, and types were completely removed in Elasticsearch 8.0. By default, when you configure a synchronization or migration task, DTS maps a table from a relational database to an index in Elasticsearch. You can change this mapping when you configure the objects to synchronize or migrate.

      Elasticsearch 7.0 and later

      Elasticsearch

      Relational database

      index

      table

      document

      row

      field

      column

      mapping

      schema

      Versions before Elasticsearch 7.0

      Elasticsearch

      Relational database

      index

      database

      type

      table

      document

      row

      field

      column

      mapping

      schema

    Procedure

    1. Go to the data synchronization task list page in the destination region. You can do this in one of two ways.

      DTS console

      1. Log on to the DTS console.

      2. In the navigation pane on the left, click Data Synchronization.

      3. In the upper-left corner of the page, select the region where the synchronization instance is located.

      DMS console

      Note

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

      1. Log on to the DMS console.

      2. In the top menu bar, choose Data + AI > DTS (DTS) > Data Synchronization.

      3. To the right of Data Synchronization Tasks, select the region of the synchronization instance.

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

    3. Configure the source and destination databases.

      Warning

      After you select the source and destination instances, review the Limits at the top of the page. Otherwise, the task may fail or data inconsistency may occur.

      Category

      Parameter

      Description

      N/A

      Task Name

      DTS automatically generates a task name. We recommend that you specify a descriptive name for easy identification. The name does not need to be unique.

      Source Database

      Database Type

      Select PolarDB-X 2.0.

      Connection Type

      Select Alibaba Cloud Instance.

      Instance Region

      Select the region where the source PolarDB-X 2.0 instance resides.

      Replicate Data Across Alibaba Cloud Accounts

      For this example, select No, as the database instance belongs to the current Alibaba Cloud account.

      Instance ID

      Select the instance ID of the source PolarDB-X 2.0 instance.

      Database Account

      Enter the database account of the source PolarDB-X 2.0 instance. The account must have the REPLICATION SLAVE, REPLICATION CLIENT, and SELECT permissions on the objects to synchronize.

      Note

      For information on how to grant permissions, see Account permission issues during data synchronization.

      Database Password

      Enter the password for the specified database account.

      Destination Database

      Database Type

      Select Elasticsearch.

      Connection Type

      Select Alibaba Cloud Instance.

      Instance Region

      Select the region where the destination Elasticsearch instance resides.

      Type

      Select Cluster Edition or Serverless.

      Instance ID

      Select the instance ID of the destination Elasticsearch instance.

      Database Account

      Enter the database account for the destination Elasticsearch instance. The account must have read and write permissions. The default account is elastic.

      Database Password

      Enter the password for the specified database account.

      Encryption

      Select HTTP or HTTPS as needed.

    4. After completing the configuration, click Test Connectivity and Proceed at the bottom of the page.

      Note

      • Ensure that you add the CIDR blocks of the DTS servers (either automatically or manually) to the security settings of both the source and destination databases to allow access. For more information, see Add the IP address whitelist of DTS servers.

      • If the source or destination is a self-managed database (i.e., the Access Method is not Alibaba Cloud Instance), you must also click Test Connectivity in the CIDR Blocks of DTS Servers dialog box.

    5. Configure the task objects.

      1. On the Configure Objects page, specify the objects to synchronize.

        Parameter

        Description

        Synchronization Types

        DTS always selects Incremental Data Synchronization. By default, you must also select Schema Synchronization and Full Data Synchronization. After the precheck, DTS initializes the destination cluster with the full data of the selected source objects, which serves as the baseline for subsequent incremental synchronization.

        Index Name

        • Table Name

          If you select Table Name, the index name in the destination Elasticsearch instance matches the table name. For example, the index name is 'order'.

        • Database Name_Table Name

          If you select Database Name_Table Name, the index name in the destination Elasticsearch instance is in the format of DatabaseName_TableName. For example, the index name is dtstest_order.

        Processing Mode of Conflicting Tables

        • Precheck and Report Errors: Checks for tables with the same names in the destination database. If any tables with the same names are found, an error is reported during the precheck and the data synchronization task does not start. Otherwise, the precheck is successful.

          Note

          If you cannot delete or rename the table with the same name in the destination database, you can map it to a different name in the destination. For more information, see Object name mapping.

        • Ignore Errors and Proceed: Skips the check for tables with the same name in the destination database.

          Warning

          Selecting Ignore Errors and Proceed may cause data inconsistency and put your business at risk. For example:

          • If the table schemas are consistent and a record in the destination database has the same primary key or unique key value as a record in the source database:

            • During full data synchronization, DTS retains the destination record and skips the source record.

            • During incremental synchronization, DTS overwrites the destination record with the source record.

          • If the table schemas are inconsistent, data initialization may fail. This can result in only partial data synchronization or a complete synchronization failure. Use with caution.

        Capitalization of Object Names in Destination Instance

        Configure the case-sensitivity policy for database, table, and column names in the destination instance. By default, the DTS default policy is selected. You can also choose to use the default policy of the source or destination database. For more information, see Case policy for destination object names.

        Source Objects

        In the Source Objects box, click the objects, and then click 向右 to move them to the Selected Objects box.

        Note

        You can select objects at the database, table, or column level. If you select only tables or columns, DTS does not synchronize other object types (such as views, triggers, and stored procedures).

        Selected Objects

        • To rename a single object in the destination instance, right-click the object in the Selected Objects box. For more information, see Map a single object name.

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

        Note

        • The only special character supported in index and type names is the underscore (_).

        • To select SQL operations to synchronize at the database or table level, right-click the object in the Selected Objects box, and then select the SQL operations.

        • To filter data by using a WHERE clause, right-click the table in the Selected Objects box and set the filter condition. For more information, see Filter task data by using SQL conditions.

        • If you use the object name mapping feature, other objects that depend on the mapped object might fail to be synchronized.

      2. Click Next: Advanced Settings.

        Parameter

        Description

        Dedicated Cluster for Task Scheduling

        By default, DTS uses a shared cluster for tasks, so you do not need to make a selection. For greater task stability, you can purchase a dedicated cluster to run the DTS synchronization task. For more information, see What is a DTS dedicated cluster?.

        Retry Time for Failed Connections

        If the connection to the source or destination database fails after the synchronization task starts, DTS reports an error and immediately begins to retry the connection. The default retry duration is 720 minutes. You can customize the retry time to a value from 10 to 1,440 minutes. We recommend a duration of 30 minutes or more. If the connection is restored within this period, the task resumes automatically. Otherwise, the task fails.

        Note

        • If multiple DTS instances (e.g., Instance A and B) share a source or destination, DTS uses the shortest configured retry duration (e.g., 30 minutes for A, 60 for B, so 30 minutes is used) for all instances.

        • DTS charges for task runtime during connection retries. Set a custom duration based on your business needs, or release the DTS instance promptly after you release the source/destination instances.

        Retry Time for Other Issues

        If a non-connection issue (e.g., a DDL or DML execution error) occurs, DTS reports an error and immediately retries the operation. The default retry duration is 10 minutes. You can also customize the retry time to a value from 1 to 1,440 minutes. We recommend a duration of 10 minutes or more. If the related operations succeed within the set retry time, the synchronization task automatically resumes. Otherwise, the task fails.

        Important

        The value of Retry Time for Other Issues must be less than that of Retry Time for Failed Connections.

        Enable Throttling for Full Data Synchronization

        During full data synchronization, DTS consumes read and write resources from the source and destination databases, which can increase their load. To mitigate pressure on the destination database, you can limit the migration rate by setting Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s).

        Note

        Enable Throttling for Incremental Data Synchronization

        You can also limit the incremental synchronization rate to reduce pressure on the destination database by setting RPS of Incremental Data Synchronization and Data synchronization speed for incremental synchronization (MB/s).

        Environment Tag

        You can select an environment tag to identify the instance. In this example, no tag is needed.

        Shard Configuration

        Set the number of primary and replica shards for the index based on the maximum shard configuration of the index in the destination Elasticsearch instance.

        String Index

        Specify how strings are indexed in the destination Elasticsearch instance.

        • analyzed: DTS analyzes the string and then indexes it. You must also select an analyzer. For more information about analyzer types and their functions, see Analyzers.

        • not_analyzed: DTS indexes the string as-is without analysis.

        • no: DTS does not index the string.

        Time Zone

        Select a time zone for time-related data types such as DATETIME and TIMESTAMP when they are synchronized to the destination Elasticsearch instance.

        Note

        If the time-related data types in the destination instance do not require a time zone, you must set the document type (type) for these data types in the destination instance before synchronization.

        DOCID

        The DOCID defaults to the primary key of the table. If the table has no primary key, the DOCID is an ID automatically generated by Elasticsearch.

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

        Choose whether DTS writes heartbeat SQL information to the source database while the instance is running.

        • Yes: Does not write heartbeat SQL information to the source database. The DTS instance may display latency.

        • No: Writes heartbeat SQL information to the source database. This may interfere with source database operations like physical backups and cloning.

        Configure ETL

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

        Monitoring and Alerting

        Choose whether to set up alerts. If the synchronization fails or the latency exceeds the specified threshold, DTS sends a notification to the alert contacts.

      3. After the configuration is complete, click Next: Configure Table And Field at the bottom of the page to set the _routing policy and _id value for the tables to synchronize to the destination Elasticsearch.

        Type

        Description

        Set _routing

        Setting _routing can route and store documents on a specific shard of the destination Elasticsearch instance. For more information, see _routing.

        • Select Yes to use custom columns for routing.

        • Select No to use _id for routing.

        Note

        If the created destination Elasticsearch instance is version 7.x, you must select No.

        _id Value

        • Primary Key Column Of The Table

          Composite primary keys are merged into one column.

        • Business Primary Key

          If you select Business Primary Key, you also need to set the corresponding Business Primary Key Column.

    6. Save the task and perform a precheck.

      • To view the parameters for configuring this instance via an API operation, hover over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the tooltip.

      • If you have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.

      Note

      • Before a synchronization task starts, DTS performs a precheck. You can start the task only if the precheck passes.

      • If the precheck fails, click View Details next to the failed item, fix the issue as prompted, and then rerun the precheck.

      • If the precheck generates warnings:

        • For non-ignorable warning, click View Details next to the item, fix the issue as prompted, and run the precheck again.

        • For ignorable warnings, you can bypass them by clicking Confirm Alert Details, then Ignore, and then OK. Finally, click Precheck Again to skip the warning and run the precheck again. Ignoring precheck warnings may lead to data inconsistencies and other business risks. Proceed with caution.

    7. Purchase the instance.

      1. When the Success Rate reaches 100%, click Next: Purchase Instance.

      2. On the Purchase page, select the billing method and link specifications for the data synchronization instance. For more information, see the following table.

        Category

        Parameter

        Description

        New Instance Class

        Billing Method

        • Subscription: You pay upfront for a specific duration. This is cost-effective for long-term, continuous tasks.

        • Pay-as-you-go: You are billed hourly for actual usage. This is ideal for short-term or test tasks, as you can release the instance at any time to save costs.

        Resource Group Settings

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

        Instance Class

        DTS offers synchronization specifications at different performance levels that affect the synchronization rate. Select a specification based on your business requirements. For more information, see Data synchronization link specifications.

        Subscription Duration

        In subscription mode, select the duration and quantity of the instance. Monthly options range from 1 to 9 months. Yearly options include 1, 2, 3, or 5 years.

        Note

        This option appears only when the billing method is Subscription.

      3. Read and select the checkbox for Data Transmission Service (Pay-as-you-go) Service Terms.

      4. Click Buy and Start, and then click OK in the OK dialog box.

        You can monitor the task progress on the data synchronization page.

    Verify synchronized index and data

    After the data synchronization task enters the Running state, you can use Kibana to connect to the Elasticsearch cluster and verify that the index and data meet your requirements. For instructions, see Log on to the Kibana console.

    Note

    If the index or data does not meet your requirements, delete the index and reconfigure the data synchronization task.