- What's New
- Product Bulletin
- Service Overview
- Billing
- Getting Started
-
User Guide
- Function Overview
- Kernel Version Notes
- Permissions Management
-
Instance Management
- Instance Statuses
- Buying a DDM instance
- Splitting Read-only and Read-Write Services
- Changing Node Class
- Scaling Out a DDM Instance
- Scaling In a DDM Instance
- Restarting a DDM Instance or an Instance Node
- Deleting Pay-per-Use Instances
- Reloading Table Data
- Changing a Parameter Template
- Modifying Parameters of a DDM Instance
- Rolling Back the Version of a DDM Instance
- Upgrading the Version of a DDM Instance
- Upgrading the DDM Engine and OS
- Connection Management
- Schema Management
- Shard Configuration
- Data Nodes
-
Parameter Template Management
- Instance Parameters
- Creating a Parameter Template
- Modifying a Custom Parameter Template
- Comparing Two Parameter Templates
- Viewing Parameter Change History
- Replicating a Parameter Template
- Applying a Parameter Template
- Viewing Application Records of a Parameter Template
- Modifying the Description of a Parameter Template
- Deleting a Parameter Template
- Account Management
- Backups and Restorations
-
Data Migration
- Overview
- Migration Evaluation
- Scenario 1: Migrating Data from an On-Premises MySQL Instance to DDM
- Scenario 2: Migrating Data from a Third-Party Cloud MySQL Instance to DDM
- Scenario 3: Migrating Data from an ECS-hosted MySQL Instance on Huawei Cloud to DDM
- Scenario 4: Exporting Data from a DDM Instance
- Scenario 5: Migrating Data from Heterogeneous Databases to DDM
- Scenario 6: Migrating Data from Huawei Cloud RDS for MySQL to DDM
- Session Management
- Slow Queries
- Monitoring and Alarm Reporting
- Task Center
- Tags
- Auditing
-
SQL Syntax
- Introduction
- DDL
- DML
- Online DDL
- Functions
- Unsupported Objects and Use Constraints
- Supported SQL Statements
- Global Sequence
- Database Management Syntax
- Advanced SQL Functions
- Quotas
-
API Reference
- Before You Start
- API Overview
- Calling APIs
-
APIs (Recommended)
-
DDM Instances
- Buying a DDM instance
- Querying DDM Instances
- Querying Details of a DDM Instance
- Modifying the Name of a DDM Instance
- Changing the Security Group of a DDM Instance
- Deleting a DDM Instance
- Restarting a DDM Instance
- Reloading Table Data
- Scaling Out a DDM Instance
- Scaling in a DDM instance
- Modifying the Read Policy of the Associated DB Instance
- Synchronizing Data Node Information
- Querying Nodes of a DDM Instance
- Querying Details of a DDM Instance Node
- Querying Parameters of a Specified DDM Instance
- Modifying Parameters of a DDM Instance
- Querying DDM Engine Information
- Querying DDM Node Classes Available in an AZ
- Changing the Node Class of a DDM Instance
- Obtaining the Instance Group Information
- Creating an Instance Group
- Schemas
- Accounts
- Monitoring
- Session Management
- Application Examples
-
DDM Instances
- Permissions Policies and Supported Actions
- Appendix
- SDK Reference
-
Best Practices
- Overview
- Formulating Sharding Rules
- Determining the Number of Shards in a Schema
- Using Broadcast and Unsharded Tables
- Transaction Models
- SQL Standards
- Migrating an Entire RDS Database to DDM
- Migrating an Entire MyCat Database to DDM
- Accessing DDM Using a JDBC Connection Pool
- Logging In to a DDM Instance Using Navicat
- Migrating Data from RDS for MySQL to DDM Using DRS
- Sharding Database and Table Data of an RDS for MySQL Instance
- Performance White Paper
-
FAQs
- General Questions
-
DDM Usage
- How Does DDM Perform Sharding?
- What Do I Do If I Fail to Connect to a DDM Instance Using the JDBC Driver?
- Why It Takes So Long Time to Export Data from MySQL Using mysqldump?
- What Do I Do If a Duplicate Primary Key Error Occurs When Data Is Imported into DDM?
- What Should I Do If an Error Message Is Returned When I Specify an Auto-Increment Primary Key During Migration?
- What Do I Do If an Error Is Reported When Parameter Configuration Does Not Time Out?
- Which Should I Delete First, a Schema or its Associated RDS Instances?
- Can I Manually Delete Databases and Accounts Remained in Data Nodes After a Schema Is Deleted?
- SQL Syntax
-
RDS-related Questions
- Is the Name of a Database Table Case-Sensitive?
- What Risky Operations on RDS for MySQL Will Affect DDM?
- How Do I Handle Data with Duplicate Primary Keys in a Table?
- How Can I Query RDS for MySQL Information by Running Command show full innodb status?
- What Should I Pay Attention to When Selecting RDS for MySQL Instance Specifications?
- Connection Management
- Resource Freezing, Release, Deletion, and Unsubscription
- Videos
-
More Documents
-
User Guide (ME-Abu Dhabi Region)
- Service Overview
- Getting Started
- Function Overview
- Instance Management
-
Parameter Template Management
- Creating a Parameter Template
- Editing a Parameter Template
- Comparing Two Parameter Templates
- Viewing Parameter Change History
- Replicating a Parameter Template
- Applying a Parameter Template
- Viewing Application Records of a Parameter Template
- Modifying the Description of a Parameter Template
- Deleting a Parameter Template
- Task Center
- Schema Management
- Account Management
- Backup Management
- Monitoring Management
- Auditing
-
SQL Syntax
- Introduction
- DDL
- DML
- Functions
- Unsupported Items
- Supported SQL Statements
- Global Sequence
- Database Management Syntax
- Advanced SQL Functions
-
FAQs
- General Questions
-
DDM Usage
- How Can I Rectify a Fault in Accessing DDM by Using the JDBC Driver?
- What Version and Parameters Should I Select?
- Why It Takes So Long Time to Export Data from MySQL Using mysqldump?
- How Should I Handle the Duplicate Primary Key Error Occurring After Data Is Imported into DDM?
- What Should I Do If an Error Message Is Returned After I Specify an Auto-Increment Primary Key?
- How Do I Handle the Error Reported When Parameter Configuration Does Not Time Out?
- Which Should I Delete First, Schema or Associated RDS DB Instances?
- Should I Manually Delete Databases and Accounts Remained in the Associated RDS DB Instances After a Schema Is Deleted?
- SQL Syntax
- RDS-related Questions
- Connection Management
-
User Guide (Kuala Lumpur Region)
- Service Overview
- Getting Started
- Function Overview
- Instance Management
-
Parameter Template Management
- Creating a Parameter Template
- Editing a Parameter Template
- Comparing Two Parameter Templates
- Viewing Parameter Change History
- Replicating a Parameter Template
- Applying a Parameter Template
- Viewing Application Records of a Parameter Template
- Modifying the Description of a Parameter Template
- Deleting a Parameter Template
- Task Center
- Schema Management
- Account Management
- Backup Management
- Monitoring Management
- Auditing
-
SQL Syntax
- Introduction
- DDL
- DML
- Functions
- Unsupported Items
- Supported SQL Statements
- Global Sequence
- Database Management Syntax
- Advanced SQL Functions
-
FAQs
- General Questions
-
DDM Usage
- How Can I Rectify a Fault in Accessing DDM by Using the JDBC Driver?
- What Version and Parameters Should I Select?
- Why It Takes So Long Time to Export Data from MySQL Using mysqldump?
- How Should I Handle the Duplicate Primary Key Error Occurring After Data Is Imported into DDM?
- What Should I Do If an Error Message Is Returned After I Specify an Auto-Increment Primary Key?
- How Do I Handle the Error Reported When Parameter Configuration Does Not Time Out?
- Which Should I Delete First, Schema or Associated RDS DB Instances?
- Should I Manually Delete Databases and Accounts Remained in the Associated RDS DB Instances After a Schema Is Deleted?
- SQL Syntax
- RDS-related Questions
- Connection Management
-
API Reference (Kuala Lumpur Region)
- Before You Start
- API Overview
- Calling APIs
-
DDM Instance Management
- Querying DDM Engine
- Querying the Quota of Classes Available in Each AZ
- Creating a DDM Instance
- Querying DDM Instances
- Viewing Details of a DDM Instance
- Modifying the Name of a DDM Instance
- Modifying the Security Group of a DDM Instance
- Deleting a DDM Instance
- Restarting a DDM Instance
- Reloading Table Data
- Scaling Out a DDM instance
- Scaling In a DDM instance
- Modifying the Read Policy of the Associated DB Instance
- Synchronizing DB Instance Data
- Querying Nodes of a DDM Instance
- Querying Details of a DDM Instance Node
- Querying Parameters of a Specified DDM Instance
- Modifying Parameters of a DDM Instance
- Schema Management
- Account Management
- Monitoring Management
- Permissions Policies and Supported Actions
- Appendix
- Change History
-
User Guide (ME-Abu Dhabi Region)
- General Reference
Copied.
Pre-check
Check items in the table below one day before performing a shard configuration task.
Pre-check Items
Item |
Purpose |
Solution to Check Failure |
---|---|---|
Table name length |
Redistributing data (for example, adding shards) will generate a temporary table whose name is longer than the original table. Ensure that the name of a temporary table does not exceed the maximum length defined by MySQL. |
Modify the table name that is too long. |
Binlog full backup time of the data node |
Whether your full backups are retained for a time period long enough |
Log in to the data node console and ensure that the full backup retention period is more than 30 days. |
Binlog enabled on data nodes |
Whether binlog is enabled to support online shard configuration |
If your data node is an RDS instance, ensure that Binlog is enabled. |
Retention period of binlogs on data nodes |
The retention period of binlogs on data nodes must be long enough. |
If your data node is an RDS instance, no further action is required. |
Broadcast table consistency |
Ensure broadcast table consistency before performing a shard configuration task. |
Contact DDM O&M personnel. |
Character set and collation of source shards |
Ensure that character set and collation are consistent before and after the shard configuration. |
Contact DDM O&M personnel. |
SQL statements for creating physical stables. |
Ensure that table structure on physical shards is consistent. |
Execute CHECK TABLE to check for table structure inconsistencies and execute ALTER to rectify the inconsistencies. |
Primary keys |
All tables in the source database have primary keys, and the sharding key is a part of the primary keys to ensure data consistency after shards are changed. |
Add primary keys for tables using ALTER if the tables have no primary keys. |
Access to DB instances |
Check whether data nodes can be connected. |
Check security group configurations. |
DB instance parameters |
The source data nodes have the same DB parameter settings as the destination data nodes. |
Modify parameter configurations on the data node console. |
DB instance storage space |
The disk space of data nodes is sufficient during shard configuration. |
Scale up storage space of data nodes.
CAUTION:
This check item is based on the estimated value that may be different from the actual value. |
DB instance time zone |
The source data nodes have the same time zone requirements as the destination data nodes. |
Modify the time zone on the data node console. |
Maximum number of physical tables |
When you add shards, each data record in the source table will be rerouted to a new physical table. It takes a long time for sharding if there are too many physical tables. Check whether the number of physical tables on each node exceeds the upper limit. |
Contact customer service. |
Common Issues and Solutions
- The shard configuration fails due to table structure inconsistency.
Solution: Execute CHECK TABLE to query table structure inconsistencies and execute ALTER TABLE to rectify the inconsistencies. Contact O&M personnel if the inconsistencies cannot be rectified using DDL, for example, the primary or unique keys cannot be modified for data reasons.
- Tables without primary keys cannot be migrated. If a table has no primary keys, it cannot be correctly located and recorded. After a retry is performed during shard configuration, duplicate data may be generated.
- If the sharding key is not part of a primary key, there may be data records (in different physical tables) with duplicate primary key values in a logical table. When these data records are redistributed, they will be routed to the same physical table, and only one record is retained because they have the same primary keys. As a result, data becomes inconsistent before and after the migration, causing the shard configuration failure.
NOTE:
This error does not occur when the primary key is a globally unique sequence and the number of shards does not change.
Solution: Rectify the data and check again.
Feedback
Was this page helpful?
Provide feedbackThank you very much for your feedback. We will continue working to improve the documentation.See the reply and handling status in My Cloud VOC.
For any further questions, feel free to contact us through the chatbot.
Chatbot