Redshift Migration Synchronization to PolarDB-X

NineData data replication supports schema, full, and incremental data synchronization from Redshift to PolarDB-X data sources.

Prerequisites

• The source and target data sources have been added to NineData. For details, see Add Data Source.

• The source data source is AWS Redshift, including provisioned clusters and Redshift Serverless.

• The target data source is Alibaba Cloud PolarDB-X.

• According to AWS documentation, if NineData accesses Redshift over the public network or across VPCs, first provide a reachable endpoint for the cluster or workgroup and allow the database port and NineData service addresses in the security group or network ACL. For details, see the AWS documents Connecting to Amazon Redshift Serverless and Configure Amazon Redshift to be publicly or privately accessible.

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

  Replication Type	Redshift (Source)	PolarDB-X (Target)
  Schema Replication	USAGE on schemas, plus SELECT on tables and views	CREATE, ALTER, DROP
  Full Replication	USAGE on schemas, plus SELECT on tables and views	SELECT, INSERT, UPDATE, DELETE, CREATE
  Incremental Replication	A high-privilege read-only account that can pass incremental prechecks and read system metadata	SELECT, INSERT, UPDATE, DELETE, CREATE

• The verified cloud-side prerequisites for this link are mainly network and permission settings. AWS documentation does not require extra Binlog- or WAL-style parameters for this link. For incremental replication, rely on the NineData precheck result.

Usage Limitations

• Before starting replication, evaluate the performance of the source and target data sources and run the task during off-peak hours whenever possible. Otherwise, full initialization can consume read and write resources on both sides and increase database load.
• It is recommended that each synchronized table has a primary key or unique constraint, and that column names are unique. Otherwise, duplicate data may be replicated.
• If the source contains many wide tables, compressed columns, or complex views, run a precheck and a sample synchronization in a test environment first.

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 Incremental task, with a specification of Micro.

• Tasks with a status of Terminated 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 Spec 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 Replication in the left navigation bar.

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

4. On the Source & Target tab, configure according to the table below and click on Next.

   Parameter	Description
   Name	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.
   Source	The data source where the synchronization object is located.
   Target	The data source that receives the synchronization object.
   Target Object Name	Select the case conversion rule for object names when migrating from the source to the target. Convert all to Lowercase: Regardless of the naming rules on the source side, the naming rules on the target side are all lowercase. Consistent with Source: Follow the naming rules on the source side. Convert all to Uppercase: Regardless of the naming rules on the source side, the naming rules on the target side are all uppercase.
   Type	Choose the content that needs to be copied to the target data source. Schema: Only synchronize the database table structure of the source data source, without synchronizing the data. Full: 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. Incremental: After the full synchronization is completed, perform incremental synchronization based on the logs of the source data source.
   If target table already exists（Required when Schema is selected）	Pre-Check Error and Stop Task: Stop the task when the same name table is detected during the pre-inspection stage. Skip and Continue Task: 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. Delete Objects and Rewrite: 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. Keep Schema and Clear Data, then Rewrite（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.
   Target Table Exists Data（Required when Schema is not selected）	Pre-Check Error and Stop Task: Stop the task when data is detected in the target table during the pre-inspection stage. Ignore existing target data and append to it.: Ignore the data when it is detected in the target table during the pre-inspection stage, and append other data. Clear target existing data before write: Delete the data when it is detected in the target table during the pre-inspection stage, and rewrite it.

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

   Parameter	Description
   Replication Objects	Choose the content that needs to be copied. You can select All Objects to copy all content from the source database, or you can select Customized Object, check the content that needs to be copied in the Source Object list, and click > to add it to the right Target Object 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 Import Config in the top right corner, then click Download Template to download the configuration file template to your local machine, edit it, and then click Upload to upload the configuration file to achieve batch import. Configuration file description:

   Parameter	Description
   source_table_name	The source table name where the object to be synchronized is located.
   destination_table_name	The target table name that receives the synchronized object.
   source_schema_name	The source Schema name where the object to be synchronized is located.
   destination_schema_name	The target Schema name that receives the synchronized object.
   source_database_name	The source database name where the object to be synchronized is located.
   target_database_name	The target database name that receives the synchronized object.
   column_list	The list of fields that need to be synchronized.
   extra_configuration	Additional 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 "Mapping" tab, select different operations based on the selected replication type, and then click on Save and Pre-Check. Click on the drop-down menu next to Object Owner to specify the owner of the object, if not selected, the default is An account with the same name as schema. If there are updates in the source and target data sources during the mapping configuration phase, you can click on the Refresh Metadata button in the top right corner of the page to refresh the information of the source and target data sources.

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

   • Not including Schema: 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.

   You can also perform the following operations:

   • Click on the Mapping & Filtering on the right side of the page to customize the column names after they are synchronized to the target data source.
   • On the Mapping & Filtering page, click on Data Filter, and configure the filtering conditions through comparison expressions. Only data that meets the filtering conditions will be synchronized to the target data source. For example, if you set the filtering condition to emp_no>=10005, then data in the emp_no column that is less than 10005 will not be synchronized to the target data source.
   • Click on the icon next to "Target Table" to search for table names and replace them with target names.
   • Enter the table name in the Search Table text box at the top right to quickly locate the target table.
   • Click Batch Configuration in the upper right corner to define general rules in bulk (such as converting table and column name case, adding prefixes or suffixes, replacements, etc.), enabling unified mapping configuration for a large number of tables and columns.

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

   tip

   • You can check Enable data consistency comparison. 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 Type you selected, the timing for starting Enable data consistency comparison is as follows:
     • Schema: Start after the structure replication is completed.
     • Schema+Full, Full: Start after the full replication is completed.
   • If the pre-inspection does not pass, you need to click on Details in the Actions column on the right side of the target inspection item to investigate the cause of the failure, manually fix it, and then click on Check Again to re-execute the pre-inspection until it passes.
   • If the Result is Warning, you can fix or ignore it according to the specific situation.

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

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

View Synchronization Results

1. Log in to the NineData Console.

2. Click on Replication > Data Replication in the left navigation bar.

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

   

   Number	Function	Description
   1	Sync Delay	The 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.
   2	Configure Alerts	After configuring alerts, the system will notify you in the way you choose when the task fails.
   3	More	Pause: Pause the task, only tasks with Running status are selectable. Duplicate: Create a new replication task with the same configuration as the current task. Terminate: 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: Delete the task. Once the task is deleted, it cannot be recovered, so please proceed with caution.
   4	Structure Replication (displayed in scenarios involving structure replication)	Displays the progress and detailed information of structure replication. Click on Log on the right side of the page: View the execution logs of structure replication. Click on on the right side of the page: View the latest information. Click on View DDL in the Actions column on the right side of the target object in the list: View SQL playback.
   5	Full Replication (displayed in scenarios involving full replication)	Displays the progress and detailed information of full replication. Click on Monitor on the right side of the page: View various monitoring indicators during full replication. During full replication, you can also click on Flow Control Settings 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 Log on the right side of the page: View the execution logs of full replication. Click on on the right side of the page: View the latest information.
   6	Incremental Replication (displayed in scenarios involving incremental replication)	Displays various monitoring indicators of incremental replication. Click on View Threads on the right side of the page: View the operations currently being executed by the current replication task, including: Thread ID: Replication tasks are executed in multiple threads, displaying the current thread number in progress. Execute SQL: Details of the SQL statement currently being executed by the current thread. Response Time: The response time of the current thread. If this value increases, it indicates that the current thread may be stuck for some reason. Event Time: The timestamp when the current thread was started. Status: The status of the current thread. Click on Flow Control Settings 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 Log on the right side of the page: View the execution logs of incremental replication. Click on on the right side of the page: View the latest information.
   7	Modify Object	Displays the modification records of synchronization objects. Click on Modify Objects on the right side of the page to configure the synchronization objects. Click on on the right side of the page: View the latest information.
   8	Data Comparison	Displays the comparison results between the source data source and the target data source. If you have not enabled data comparison, please click on Enable Comparison on the page. Click on Re-compare on the right side of the page: Re-initiate the comparison between the current source and target data sources. Click on Stop 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 Log on the right side of the page: View the execution logs of consistency comparison. Click on Monitor (displayed only in data comparison): View the trend chart of RPS (records per second) comparison. Click on Details to view earlier records. Click on in the Actions column on the right side of the comparison list (displayed under the Data tab only in the case of inconsistency): View details of the comparison between the source and target sides. Click on in the Actions 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.
   9	Expand	Display detailed information of the current replication task. Common Options: Export table configuration: 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. Alert Rules: Configure the alarm strategy for the current task.

Appendix: Pre-Check Item List

Check Item	Check Content
Source data source connection check	Check the gateway status of the source data source, whether the instance is reachable, and whether the username and password are correct
Target data source connection check	Check the gateway status of the target data source, whether the instance is reachable, and whether the username and password are correct
Source database permission check	Check whether the source account has the required permissions
Target database permission check	Check whether the target account has the required permissions
Target data existence check	Check whether data already exists in the target objects to be synchronized
Target same-name object existence check	Check whether objects with the same name already exist in the target database
Source and target version check	Check whether the source and target versions are compatible
Cyclic replication check	Check whether a replication loop exists

Related Documentation

Introduction to Data Replication