MySQL Replication to TiDB

NineData data replication supports data migration or synchronization between MySQL and TiDB 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 must be added to NineData. See Add Data Source for instructions on how to add them.
The source data source must have Binlog enabled, and the Binlog-related parameters set as follows:
- binlog_format=ROW
- binlog_row_image=FULL
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If the source data source is a slave, to ensure the complete Binlog log is obtained, the log_slave_updates parameter also needs to be enabled.

Usage Limitations

The data replication function is only for the user databases in the data source, and the system databases will not be replicated. For example: information_schema, mysql, performance_schema, sys databases in MySQL type data sources will not be replicated.
The account for source data must have SELECT (for replicate database structure and full data), SHOW VIEW (for replicate views), and REPLICATION CLIENT, REPLICATION SLAVE (for replicate incremental data) privileges on the objects to be replicated. The account for target must have DML and DDL privileges.
Before performing data synchronization, user need to evaluate the performance of the source data source and the target data source, and it is recommended to perform data synchronization during off-peak time. Otherwise, the full data initialization will occupy a certain amount of read and write resources of the source data source and the target data source, increasing database load.
During the synchronization process, if the source data contains views, functions, stored procedures, triggers, and events, after synchronizing to the target data source, the definer of the above objects information will be modified in the target data source to the account that accesses the target data source in the current synchronization task.
It is necessary to ensure that each table in the synchronization object has a primary key or unique constraint, and the column name is unique, otherwise the same data may be synchronized repeatedly.
During the synchronization process, if there are triggers in the source, the system will not synchronize the triggers until the incremental synchronization ends.

Operations

Log in to the NineData Console.
Click on Replication in the left navigation bar.
On the Replication page, click on the Create Replication in the top right corner.

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. For easy retrieval and management, use a meaningful name, up to 64 characters.
Source	The data source where the sync object is located.
Target	The data source that receives the sync object.
Type	Choose the content to be copied to the target data source. Schema: Only syncs the table structure of the source data source, without syncing data. Full: Syncs all objects and data from the source data source, i.e., full data replication. The switch on the right is for toggling periodic full replication. For more information, please refer to Periodic Full Replication. Incremental: After full sync, perform incremental sync based on the log of the source data source. The icon represents incremental operation type configuration (not supported by some replication links). You can deselect certain operation types as needed. Once deselected, these operations will be ignored during incremental synchronization.
Target Table Preparation	If target table already exists (selected when Schema is selected) Pre-Check Error and Stop Task: Stop the task when a table with the same name is detected during precheck. Skip and Continue Task: Send a prompt when a table with the same name is detected during precheck and continue the task. During structure replication, ignore this table with the same name. If you are also performing data replication, data will be appended to this table with the same name without overwriting existing data. Delete Objects and Rewrite: Send a prompt when a table with the same name is detected during precheck and continue the task. During structure replication, delete the table with the same name in the target database and replicate the table structure based on the source database. If you are also performing data replication, data will be written after the table structure replication is completed. Keep Schema and Clear Data, then Rewrite (optional when performing both structure and data replication): Send a prompt when a table with the same name is detected during precheck and continue the task. During structure replication, keep the table structure in the target database and, when data replication starts, clear the data in the table with the same name and then replicate 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 exists in the target table during precheck. Ignore the existing data and append : Ignore this part of the data when data is detected in the target table during precheck and append other data. Clear the existing data before write: Delete this part of the data when data is detected in the target table during precheck and rewrite it.

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

Parameter	Description
Replication Objects	Choose what to copy. You can choose All Objects to copy all contents of the source database, or choose Customized Object to select the contents to be copied in the Source Object list and click > to add them to the right Target Object list.

If you need to create multiple identical replication links, you can create a configuration file and import it when creating a new task. Click Import Config at the top right corner, then click Download Template to download the configuration file template to your local machine. After editing, click Upload to upload the configuration file for batch import.

Parameter	Description
`source_table_name`	Name of the source table containing the objects to be synchronized.
`destination_table_name`	Name of the target table receiving the synchronized objects.
`source_schema_name`	Name of the source schema containing the objects to be synchronized.
`destination_schema_name`	Name of the target schema receiving the synchronized objects.
`source_database_name`	Name of the source database containing the objects to be synchronized.
`target_database_name`	Name of the target database receiving the synchronized objects.
`column_list`	List of columns 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.

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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.

On the Mapping tab, select different actions based on the selected replication type. If updates occur in the source and target data sources during the configuration mapping phase, you can click the Refresh Metadata button in the upper right corner of the page to refresh the information of the source and target data sources.
- Includes Schema: Configure the table name after the target table is synchronized to the target data source, and click Save and Pre-Check.
- Excludes Schema: The system automatically selects the same name database in the target data source by default. If it does not exist, you need to manually select the target database. The table names and column names in the target database need to be consistent with the sync objects. If they are not consistent, you can manually map the table names and column names.
You can also perform the following operations:
- Click on the on the right side of the page to customize the column names after they are synchronized to the target data source.
- On the page, click on , 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 to search for table names and replace them with target names.
- Enter the table name in the text box at the top right to quickly locate the target table.
- Click 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.
On the Pre-check tab, wait for the system to complete the precheck. After the precheck passes, click on Launch.
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- You can check Enable data consistency comparison. After the sync task is completed, automatically initiate data consistency comparison based on the source data source to ensure data consistency on both ends. Depending on your choice of Type, the timing of starting Enable data consistency comparison is as follows:
  - Schema: Initiated after structure replication is completed.
  - Schema + Full, Full: Initiated after full replication is completed.
  - Schema + Full + Incremental, Incremental: Initiated when the incremental data is first consistent with the source data source and Delay is 0 seconds. You can click on View Details to view the synchronization delay on the Details page.
- If the precheck fails, click on Details on the right side of the target check item to investigate the cause of the failure, manually fix it, and then click Check Again to re-execute the precheck until it passes.
- Items in Result with Warning can be repaired or ignored depending on the specific situation.
On the Launch page, when prompted with Launch Successfully, the sync task begins to run. At this point, you can perform the following operations:
- Click on View Details to view the execution status of each stage of the sync task.
- Click on Back to list to return to the Replication task list page.

View Synchronization Results

Log in to the NineData Console.
Click on Replication > Data Replication in the left navigation bar.

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

result

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. For more information, please refer to Operations Monitoring Introduction.
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 1: Mapping Table of MySQL and TiDB Data Types

Category	MySQL Data Type	TiDB Data Type
Numeric	TINYINT	TINYINT
	TINYINT UNSIGNED	TINYINT UNSIGNED
	SMALLINT	SMALLINT
	SMALLINT UNSIGNED	SMALLINT UNSIGNED
	MEDIUMINT	MEDIUMINT
	MEDIUMINT UNSIGNED	MEDIUMINT UNSIGNED
	INT	INT
	INT UNSIGNED	INT UNSIGNED
	BIGINT	BIGINT
	BIGINT UNSIGNED	BIGINT UNSIGNED
	BIT(M)	BIT(M)
	DECIMAL()	DECIMAL()
	NUMERIC	DECIMAL()
	FLOAT	FLOAT
	DOUBLE	DOUBLE
	BOOL, BOOLEAN	TINYINT
DATE AND TIME	DATE	DATE
	DATETIME[(fsp)]	DATETIME[(fsp)]
	TIMESTAMP[(fsp)]	TIMESTAMP[(fsp)]
	TIME[(fsp)]	TIME[(fsp)]
STRING	YEAR[(4)]	YEAR[(4)]
	CHAR	CHAR
	VARCHAR	VARCHAR
	BINARY/VARBINARY	BINARY/VARBINARY
	TINYTEXT/TEXT/MEDIUMTEXT/LONGTEXT	TINYTEXT/TEXT/MEDIUMTEXT/LONGTEXT
	TINYBLOB/BLOB/MEDIUMBOLB/LONGBLOB	TINYBLOB/BLOB/MEDIUMBOLB/LONGBLOB
	ENUM	ENUM
	SET	SET
JSON	JSON	JSON
SPATIAL	GEOMETRY	GEOMETRY
	GEOMCOLLECTION/GEOMTRYCOLLECTION	GEOMCOLLECTION/GEOMTRYCOLLECTION
	POINT	TEXT
	LINESTRING	TEXT
	POLYGON	TEXT
	MULTIPOINT	TEXT
	MULTIPOLYGON	TEXT
	MULTILINESTRING	TEXT

Appendix 2: Pre-check Item Overview

Check Item	Check Content
Target database data existence check	Check whether the object to be replicated not empty in the target database
Objects with the same name in the target database existence check	Check whether the object to be replicated already exists in the target database
Existence check for the Definer of non-table objects	Check whether the definer of view, trigger, procedure, function, event exists in the target database
Source datasource connection check	Check the status of the gateway of the source datasource, database connectable, and verify the username and password
Target datasource connection check	Check the status of the gateway of the target datasource, database connectable, and verify the username and password
Target databse privilege check	Check whether the account privileges of the target database meet the requirements
Source database privilege check	Check whether the account privileges of the source database meet the requirements
Source and target datasource collation check	Check whether the collations of the source and target databases are compatible
Target datasource trigger check	Check the existence of triggers on the target database
Source database log_slave_updates check	When the source database is a slave, check whether log_slave_updates is ON
Source and target datasource version check	Check whether the source and target database versions are compatible
Check if the source database has Binlog enabled	Check if the source database has Binlog enabled
Source database binlog format check	Check whether the binlog format of the source database is 'ROW'
Source database binlog_row_image check	Check whether the binlog_row_image of the source database is 'FULL'
Source and target datasource time zone check	Check whether the timezones of the source and target databases match
Source and target datasource character set check	Check whether the character set of the source and target databases are compatible
Source and target datasource SQL_MODE check	Check whether the SQL_MODE of the source and target databases are compatible
Source and target datasource case-sensitive check	Check whether the case-sensitive configurations of the source database and the target database are compatible
Source datasource and target datasource explicit_defaults_for_timestamp check	Check whether the explicit_defaults_for_timestamp of the source database and the target database are compatible
Source database procedure and function check	Check that the source database has been granted privileges to obtain the definitions of procedures and functions

Introduction to Data Replication

MySQL Replication to TiDB

Feature Introduction​

Prerequisites​

Usage Limitations​

Operations​

View Synchronization Results​

Appendix 1: Mapping Table of MySQL and TiDB Data Types​

Appendix 2: Pre-check Item Overview​

Related Documents​