- Release Notes and Announcements
- Release Notes
- Announcements
- Announcement on Change of Part of Parameters
- Announcement on Update of Database Audit Feature
- Announcement on Authentication of a Newly Added API Interface of Database Audit
- Announcement on Change of Public Network Linkage
- TDSQL-C for MySQL Audit Service Update
- Emergency Fix for Certain Monitoring Metrics
- Monitoring Metric Optimization
- Some AZs Are Sold Out
- Change to Database Audit Resource ID
- Ops Change
- Storage Price Adjustment Notification
- Product Introduction
- Kernel Features
- Purchase Guide
- Getting Started
- Database Audit
- Serverless Service
- Operation Guide
- Switching Cluster Page View in Console
- Database Connection
- Instance Management
- Configuration Adjustment
- Cluster Management
- Scaling Instance
- Database Proxy
- Database Proxy Overview
- Use Limits
- Database Proxy Kernel Features
- Managing Database Proxy
- Enabling Database Proxy
- Setting Database Proxy Address
- Modifying or Deleting Connection Addresses
- Viewing and Changing the Access Policy
- Rebalancing the Load
- Transaction Split Feature
- Access Mode
- Adjusting Database Proxy Configuration
- Switching Database Proxy Network
- Viewing Database Proxy Monitoring Data
- Disabling Database Proxy
- Automatic Read/Write Separation
- Connection Pool Feature
- Other Features
- Account Management
- Database Management
- Database Management Tool
- Columnar Storage Index (CSI)
- Parameter Configuration
- Multi-AZ Deployment
- Backup and Restoration
- Operation Log
- Data Migration
- Parallel Query
- Database Security and Encryption
- Monitoring and Alarms
- Basic SQL Operations
- Connecting to TDSQL-C for MySQL Through SCF
- Tag
- Best Practices
- White Paper
- API Documentation
- History
- Introduction
- API Category
- Making API Requests
- Instance APIs
- CloseClusterPasswordComplexity
- CopyClusterPasswordComplexity
- DescribeClusterPasswordComplexity
- ModifyClusterPasswordComplexity
- OpenClusterPasswordComplexity
- UpgradeClusterVersion
- UpgradeInstance
- SetRenewFlag
- OfflineCluster
- ModifyMaintainPeriodConfig
- IsolateInstance
- IsolateCluster
- DescribeMaintainPeriod
- DescribeInstanceSpecs
- DescribeClusters
- DescribeClusterDetail
- CreateClusters
- AddInstances
- OfflineInstance
- DescribeInstanceDetail
- DescribeClusterInstanceGrps
- DescribeInstances
- ActivateInstance
- ModifyInstanceName
- ModifyClusterName
- SearchClusterTables
- SearchClusterDatabases
- RestartInstance
- Multi-AZ APIs
- Account APIs
- Audit APIs
- Database Proxy APIs
- Backup and Restoration APIs
- Parameter Management APIs
- Performance Analysis APIs
- Billing APIs
- Serverless APIs
- ResourcePackage APIs
- Other APIs
- CloseWan
- CreateClusterDatabase
- DeleteClusterDatabase
- DescribeClusterDetailDatabases
- ModifyClusterDatabase
- OpenWan
- OpenClusterReadOnlyInstanceGroupAccess
- OpenReadOnlyInstanceExclusiveAccess
- ModifyDBInstanceSecurityGroups
- DescribeProjectSecurityGroups
- DescribeDBSecurityGroups
- SwitchProxyVpc
- DescribeFlow
- DescribeZones
- SwitchClusterVpc
- ModifyVipVport
- Data Types
- Error Codes
- FAQs
- TDSQL-C Policy
- Glossary
- Contact Us
- Release Notes and Announcements
- Release Notes
- Announcements
- Announcement on Change of Part of Parameters
- Announcement on Update of Database Audit Feature
- Announcement on Authentication of a Newly Added API Interface of Database Audit
- Announcement on Change of Public Network Linkage
- TDSQL-C for MySQL Audit Service Update
- Emergency Fix for Certain Monitoring Metrics
- Monitoring Metric Optimization
- Some AZs Are Sold Out
- Change to Database Audit Resource ID
- Ops Change
- Storage Price Adjustment Notification
- Product Introduction
- Kernel Features
- Purchase Guide
- Getting Started
- Database Audit
- Serverless Service
- Operation Guide
- Switching Cluster Page View in Console
- Database Connection
- Instance Management
- Configuration Adjustment
- Cluster Management
- Scaling Instance
- Database Proxy
- Database Proxy Overview
- Use Limits
- Database Proxy Kernel Features
- Managing Database Proxy
- Enabling Database Proxy
- Setting Database Proxy Address
- Modifying or Deleting Connection Addresses
- Viewing and Changing the Access Policy
- Rebalancing the Load
- Transaction Split Feature
- Access Mode
- Adjusting Database Proxy Configuration
- Switching Database Proxy Network
- Viewing Database Proxy Monitoring Data
- Disabling Database Proxy
- Automatic Read/Write Separation
- Connection Pool Feature
- Other Features
- Account Management
- Database Management
- Database Management Tool
- Columnar Storage Index (CSI)
- Parameter Configuration
- Multi-AZ Deployment
- Backup and Restoration
- Operation Log
- Data Migration
- Parallel Query
- Database Security and Encryption
- Monitoring and Alarms
- Basic SQL Operations
- Connecting to TDSQL-C for MySQL Through SCF
- Tag
- Best Practices
- White Paper
- API Documentation
- History
- Introduction
- API Category
- Making API Requests
- Instance APIs
- CloseClusterPasswordComplexity
- CopyClusterPasswordComplexity
- DescribeClusterPasswordComplexity
- ModifyClusterPasswordComplexity
- OpenClusterPasswordComplexity
- UpgradeClusterVersion
- UpgradeInstance
- SetRenewFlag
- OfflineCluster
- ModifyMaintainPeriodConfig
- IsolateInstance
- IsolateCluster
- DescribeMaintainPeriod
- DescribeInstanceSpecs
- DescribeClusters
- DescribeClusterDetail
- CreateClusters
- AddInstances
- OfflineInstance
- DescribeInstanceDetail
- DescribeClusterInstanceGrps
- DescribeInstances
- ActivateInstance
- ModifyInstanceName
- ModifyClusterName
- SearchClusterTables
- SearchClusterDatabases
- RestartInstance
- Multi-AZ APIs
- Account APIs
- Audit APIs
- Database Proxy APIs
- Backup and Restoration APIs
- Parameter Management APIs
- Performance Analysis APIs
- Billing APIs
- Serverless APIs
- ResourcePackage APIs
- Other APIs
- CloseWan
- CreateClusterDatabase
- DeleteClusterDatabase
- DescribeClusterDetailDatabases
- ModifyClusterDatabase
- OpenWan
- OpenClusterReadOnlyInstanceGroupAccess
- OpenReadOnlyInstanceExclusiveAccess
- ModifyDBInstanceSecurityGroups
- DescribeProjectSecurityGroups
- DescribeDBSecurityGroups
- SwitchProxyVpc
- DescribeFlow
- DescribeZones
- SwitchClusterVpc
- ModifyVipVport
- Data Types
- Error Codes
- FAQs
- TDSQL-C Policy
- Glossary
- Contact Us
TDSQL-C for MySQL allows you to enable or disable the parallel query feature by adjusting parameters. Specifically, you can enable or disable the feature for all SQL statements, set execution conditions, or specify the execution mode of a specific SQL statement through the HINT statement in the console.
Note:
The HINT statement can specify whether to execute a SQL statement and apply session parameters to the statement. In addition, it also supports querying the specified parallel table.
HINT statement usage
Feature | Command Line | Description |
Enable parallel query | SELECT /*+PARALLEL(x)*/ ... FROM ...; | x indicates the parallelism for the SQL statement, which should be greater than 0. |
Disable parallel query | SELECT /*+PARALLEL(x)*/ ... FROM ...; | If x is set to 0, it indicates to disable parallel query. |
Specify the parallel table | You can specify the table to be included in or excluded from the parallel query execution plan in either of the following ways: Specify the table to be included in the plan through PARALLEL. SELECT /*+PARALLEL(t)*/ ... FROM ...;Specify the table to be excluded from the plan through NO_PARALLEL. SELECT /*+NO_PARALLEL(t)*/ ... FROM ...; | t is the table name. |
Specify both the parallel table and parallelism | SELECT /*+PARALLEL(t x)*/ * ... FROM ...; | x indicates the parallelism for the SQL statement, which should be greater than 0. t is the table name. |
Set the session parameter through the HINT statement, which takes effect only for the specified SQL statement | SELECT /*+SET_VAR(var=n)*/ * ... FROM ...; | var is the parallel query parameter in the session scope. |
HINT statement use cases
Use case 1:
select /*+PARALLEL()*/ * FROM t1,t2;
Set the parallelism to the value of txsql_parallel_degree (default) for the parallel query. If a statement does not meet the parallel query execution condition, serial query will be used.Use case 2:
select /*+PARALLEL(4)*/ * FROM t1,t2;
Set the parallelism of the statement to 4 regardless of the default value, i.e., txsql_parallel_degree = 4. If the statement does not meet the parallel query execution condition, serial query will be used.Use case 3:
select /*+PARALLEL(t1)*/ * FROM t1,t2;
Include the t1 table in the parallel query and use the default parallelism. If t1 is smaller than the value of txsql_parallel_table_record_threshold, serial query will be used.Use case 4:
select /*+PARALLEL(t1 8)*/ * FROM t1,t2;
Include the t1 table in the parallel query and set the parallelism to 8. If t1 is smaller than the value of txsql_parallel_table_record_threshold, serial query will be used.Use case 5:
select /*+NO_PARALLEL(t1)*/ * FROM t1,t2;
Exclude the t1 table from the parallel query. If t1 is greater than the value of txsql_parallel_table_record_threshold, serial query will be used.Use case 6:
select /*+SET_VAR(txsql_parallel_degree=8)*/ * FROM t1,t2;
Set the parallelism of the statement to 8 regardless of the default value, i.e., txsql_parallel_degree = 8.Use case 7:
select /*+SET_VAR(txsql_parallel_cost_threshold=1000)*/ * FROM t1,t2
Set txsql_parallel_cost_threshold=1000 for the statement. If its execution penalty is greater than 1000, parallel query can be used.Use case 8:
select /*+SET_VAR(txsql_optimizer_context_max_mem_size=500000)*/ * FROM t1,t2
Set txsql_optimizer_context_max_mem_size=500000 for a statement, which means to adjust the maximum memory size it can apply for in the parallel query plan environment to 500000.
Yes
No
Was this page helpful?