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SQL Server Migration Synchronization to PolarDB PostgreSQL

NineData data replication supports data synchronization between SQL Server and Alibaba Cloud PolarDB for PostgreSQL data sources.

Feature Introduction​

NineData data replication supports high-performance replication of structure, full data, and incremental data between data sources. For certain data sources, it also provides bidirectional replication, enabling the quick construction of geo-distributed active-active business architectures.

  • Structure: Supports the replication of object structures between homogeneous and heterogeneous data sources, greatly reducing the barrier to data replication between two sources.
  • Full Data: Achieves row-level concurrent batch replication through intelligent data sharding, effectively ensuring replication performance. The independently developed novel breakpoint resume technology ensures the accuracy of data in tables without primary keys.
  • Incremental Data: Supports DML and DDL incremental data replication for all object types. By leveraging technologies such as row-level concurrency and hotspot merging, it delivers robust replication performance.
  • Bidirectional Real-time Data Replication (only between MySQL instances): Direct bidirectional replication of data between multiple nodes ensures that all node data remains up-to-date.

With the above features, it is easy and efficient to achieve scenarios such as full|incremental data replication, full|incremental data migration, full|incremental data synchronization, data integration, and seamless migration without downtime, providing enterprises with flexible and reliable data replication solutions.

Prerequisites​

  • The source and target data sources have been added to NineData. For instructions on how to add them, see Add Data Source.

  • The source data source is SQL Server, with a version of 2022, 2019, 2017, 2016, 2014, 2012, 2008R2, or 2008.

  • The target is Alibaba Cloud PolarDB for PostgreSQL.

  • You must have the following permissions for the source and target data sources:

    Replication Type
    		Source Data SourceTarget Data Source
    Full ReplicationRead PermissionSELECT, INSERT, UPDATE, DELETE Permissions
    Incremental ReplicationOwner PermissionSELECT, INSERT, UPDATE, DELETE Permissions

Usage Limitations​

  • Before performing data synchronization, it is necessary to assess the performance of the source and target data sources, and it is recommended to perform data synchronization during off-peak business hours. Otherwise, the full data initialization will occupy a certain amount of read and write resources of the source and target data sources, leading to increased database load.
  • It is necessary to ensure that each table in the synchronization object has a primary key or unique constraint, and the column names are unique; otherwise, the same data may be synchronized repeatedly.

Operation Steps​

Commercialization Notice

NineData’s data replication product has been commercialized. You can still use 10 replication tasks for free, with the following considerations:

  • Among the 10 replication tasks, you can include 1 task, with a specification of Micro.

  • Tasks with a status of do not count towards the 10-task limit. If you have already created 10 replication tasks and want to create more, you can terminate previous replication tasks and then create new ones.

  • When creating replication tasks, you can only select the you have purchased. Specifications that have not been purchased will be grayed out and cannot be selected. If you need to purchase additional specifications, please contact us through the customer service icon at the bottom right of the page.

  1. Log in to the NineData Console.

  2. Click on in the left navigation bar.

  3. On the page, click on in the top right corner.

  4. On the tab, configure according to the table below and click on .

    Parameter
    		Description
    Enter the name of the data synchronization task. To facilitate subsequent search and management, please use a meaningful name. Up to 64 characters are supported.
    The data source where the synchronization object is located.
    The data source that receives the synchronization object.
    Select the case conversion rule for object names when migrating from the source to the target.
    • : Regardless of the naming rules on the source side, the naming rules on the target side are all lowercase.
    • : Follow the naming rules on the source side.
    • : Regardless of the naming rules on the source side, the naming rules on the target side are all uppercase.
    Choose the content that needs to be copied to the target data source.
    • : Only synchronize the database table structure of the source data source, without synchronizing the data.
    • : Synchronize all objects and data of the source data source, that is, full data replication. The switch on the right is for periodic full replication. For more information, please refer to Periodic Full Replication.
    • : After the full synchronization is completed, perform incremental synchronization based on the logs of the source data source.
    （Required when is selected）
    • : Stop the task when the same name table is detected during the pre-inspection stage.
    • : Send a prompt and continue the task when the same name table is detected during the pre-inspection stage. During structure replication, ignore the table with the same name. If you also perform data replication, the data will be appended to the table with the same name without overwriting the existing data.
    • : Send a prompt and continue the task when the same name table is detected during the pre-inspection stage. During structure replication, delete the table with the same name in the target database and re-copy the table structure based on the source database. If you also perform data replication, the data will be written after the table structure is copied.
    • （Optional when both structure and data replication are performed）: Send a prompt and continue the task when the same name table is detected during the pre-inspection stage. During structure replication, retain the table structure in the target database, and clear the data in the table with the same name at the beginning of data replication, then re-copy from the original table.
    （Required when is not selected）
    • : Stop the task when data is detected in the target table during the pre-inspection stage.
    • : Ignore the data when it is detected in the target table during the pre-inspection stage, and append other data.
    • : Delete the data when it is detected in the target table during the pre-inspection stage, and rewrite it.

  5. On the tab, configure the following parameters, and then click on .

    Parameter
    		Description
    Choose the content that needs to be copied. You can select to copy all content from the source database, or you can select , check the content that needs to be copied in the list, and click > to add it to the right list.

    If you need to create multiple replication chains with the same replication object, you can create a configuration file and import it when creating a new task. Click on in the top right corner, then click Download Template to download the configuration file template to your local machine, edit it, and then click to upload the configuration file to achieve batch import. Configuration file description:

    Parameter
    		Description
    source_table_nameThe source table name where the object to be synchronized is located.
    destination_table_nameThe target table name that receives the synchronized object.
    source_schema_nameThe source Schema name where the object to be synchronized is located.
    destination_schema_nameThe target Schema name that receives the synchronized object.
    source_database_nameThe source database name where the object to be synchronized is located.
    target_database_nameThe target database name that receives the synchronized object.
    column_listThe list of fields that need to be synchronized.
    extra_configurationAdditional configuration information can be set here:
    • column_rules: Used to define column mapping and value rules. Field descriptions:
      • column_name: Original column name.
      • destination_column_name: Target column name.
      • column_value: Value to assign, which can be an SQL function or a constant.
    • filter_condition: Used to specify row-level filtering conditions; only rows that meet the criteria will be copied.
    tip

    • An example of the extra_configuration content is as follows:

      {
        "extra_config": {
          "column_rules": [
            {
              "column_name": "created_time", // Original column name to map.
              "destination_column_name": "migrated_time", // Target column name mapped to "migrated_time".
              "column_value": "current_timestamp()" // Change the column value to the current timestamp.
            }
          ],
          "filter_condition": "id != 0" // Only rows where ID is not 0 will be synchronized.
        }
      }

    • For a complete example of the configuration file, refer to the downloaded template.

    :::

  6. On the tab, select different operations based on the selected replication type, and then click on . Click on the drop-down menu next to Object Owner to specify the owner of the object, if not selected, the default is . If there are updates in the source and target data sources during the mapping configuration phase, you can click on the button in the top right corner of the page to refresh the information of the source and target data sources.

    • Including : Configure the table name after the target table is synchronized to the target data source.

    • Not including : The system defaults to selecting the database with the same name in the target data source, if it does not exist, you need to manually select the target library. The table name and column name in the target library need to be consistent with the synchronization object. If they are not consistent, you can also manually map the table name and column name.

    您还可以进行如下操作：

    • 单击页面右侧的，自定义列名同步到目标数据源之后的名称。
    • 在页面，单击，通过比较表达式配置过滤条件，仅符合过滤条件的数据会同步到目标数据源。例如，将过滤条件设置为 emp_no>=10005，则 emp_no 列中小于 10005 的数据均不会同步到目标数据源。
    • 单击右侧的replace_tablename图标，可搜索表名，并替换成目标名称。
    • 在右上角的文本框中输入表名以快速定位到目标表。
    • 单击右上角的，可以批量定义通用规则（如表名、字段名大小写转换、前后缀添加、替换等），实现对大量表和字段的统一映射配置。

  7. On the tab, wait for the system to complete the pre-inspection, and after the pre-inspection is passed, click on .

    tip
    • You can check . After the synchronization task is completed, automatically start a data consistency comparison based on the source data source to ensure data consistency on both sides. Depending on the you selected, the timing for starting is as follows:
      • : Start after the structure replication is completed.
      • +, : Start after the full replication is completed.
    • If the pre-inspection does not pass, you need to click on in the column on the right side of the target inspection item to investigate the cause of the failure, manually fix it, and then click on to re-execute the pre-inspection until it passes.
    • If the is , you can fix or ignore it according to the specific situation.

  8. On the page, it prompts , and the synchronization task starts running. At this point, you can perform the following operations:

    • Click on to view the execution of each stage of the synchronization task.
    • Click on to return to the task list page.

View Synchronization Results​

  1. Log in to the NineData Console.

  2. Click on > in the left navigation bar.

  3. On the page, click on the of the target synchronization task, the page details are as follows.

    result

    Number
    		Function
    		Description
    1Sync DelayThe data synchronization delay between the source data source and the target data source. 0 seconds means there is no delay between the two ends, at which point you can choose to switch the business to the target data source for smooth migration.
    2Configure AlertsAfter configuring alerts, the system will notify you in the way you choose when the task fails. For more information, please refer to Operations Monitoring Introduction.
    3More
    • : Pause the task, only tasks with Running status are selectable.
    • : Create a new replication task with the same configuration as the current task.
    • : End tasks that are unfinished or listening (i.e., in incremental synchronization). Once the task is terminated, it cannot be restarted, so please proceed with caution. If the synchronization objects contain triggers, a trigger replication option will pop up, please select as needed.
    • : Delete the task. Once the task is deleted, it cannot be recovered, so please proceed with caution.
    4Structure Replication (displayed in scenarios involving structure replication)Displays the progress and detailed information of structure replication.
    • Click on on the right side of the page: View the execution logs of structure replication.
    • Click on refresh on the right side of the page: View the latest information.
    • Click on in the column on the right side of the target object in the list: View SQL playback.
    5Full Replication (displayed in scenarios involving full replication)Displays the progress and detailed information of full replication.
    • Click on on the right side of the page: View various monitoring indicators during full replication. During full replication, you can also click on on the right side of the monitoring indicator page to limit the rate of writing to the target data source per second. The unit is rows/second.
    • Click on on the right side of the page: View the execution logs of full replication.
    • Click on refresh on the right side of the page: View the latest information.
    6Incremental Replication (displayed in scenarios involving incremental replication)Displays various monitoring indicators of incremental replication.
    • Click on on the right side of the page: View the operations currently being executed by the current replication task, including:
      • : Replication tasks are executed in multiple threads, displaying the current thread number in progress.
      • : Details of the SQL statement currently being executed by the current thread.
      • : The response time of the current thread. If this value increases, it indicates that the current thread may be stuck for some reason.
      • : The timestamp when the current thread was started.
      • : The status of the current thread.
    • Click on on the right side of the page: Limit the rate of writing to the target data source per second. The unit is rows/second.
    • Click on on the right side of the page: View the execution logs of incremental replication.
    • Click on refresh on the right side of the page: View the latest information.
    7Modify ObjectDisplays the modification records of synchronization objects.
    • Click on on the right side of the page to configure the synchronization objects.
    • Click on refresh on the right side of the page: View the latest information.
    8Data ComparisonDisplays the comparison results between the source data source and the target data source. If you have not enabled data comparison, please click on on the page.
    • Click on on the right side of the page: Re-initiate the comparison between the current source and target data sources.
    • Click on on the right side of the page: After the comparison task starts, you can click this button to stop the comparison task immediately.
    • Click on on the right side of the page: View the execution logs of consistency comparison.
    • Click on (displayed only in data comparison): View the trend chart of RPS (records per second) comparison. Click on to view earlier records.
    • Click on details in the column on the right side of the comparison list (displayed under the tab only in the case of inconsistency): View details of the comparison between the source and target sides.
    • Click on sql in the column on the right side of the comparison list (displayed only in the case of inconsistency): Generate change SQL. You can directly copy this SQL to the target data source to execute and modify the inconsistent content.
    9ExpandDisplay detailed information of the current replication task. Common Options:
    • : Export the current task's database and table configuration, allowing for quick import when creating a new replication task. This helps rapidly establish multiple replication links with the same replication objects.
    • : Configure the alarm strategy for the current task.

Appendix: Pre-Check Item List​

Check ItemsCheck Contents
Target databse privilege checkCheck whether the account privileges of the target database meet the requirements
Objects with the same name in the target database existence checkCheck whether the object to be replicated already exists in the target database
Source datasource connection checkCheck the status of the gateway of the source datasource, database connectable, and verify the username and password
Target datasource connection checkCheck the status of the gateway of the target datasource, database connectable, and verify the username and password
Source database privilege checkCheck whether the account privileges of the source database meet the requirements
Source and target datasource version checkCheck whether the source and target database versions are compatible
Target database data existence checkCheck whether the object to be replicated not empty in the target database
Cyclic replication checkCheck for replication loops
Source DB configuration checkCheck if the source db complies with incremental log reading
Check the read-only status of the target database instanceCheck the read-only status of the target database instance

Data Replication Introduction