- Release Notes and Announcements
- Release Notes
- Announcements
- Announcement on the Rule-Based Audit Feature for Database Audit
- Announcement on Some APIs with CAM Authentication Integrated
- Announcement on Some APIs with CAM Authentication Integrated
- Notice on Elimination of Some Indicators in Event Alarms
- Commercial Billing for Database Proxy
- TencentDB for MySQL Audit Upgrade
- Added Authentication APIs
- API Authentication Upgrade
- TencentDB for MySQL API 2.0 Discontinuation
- Monitoring Module Upgrade in Shanghai Region
- Monitoring Metric Optimization
- Network Architecture Upgrade
- Change of APIs for Querying the Specifications of Purchasable Database Instances
- Replacement of Certain Old Database Proxy APIs
- Added Advanced Monitoring Metrics
- Change of Calculation Formula for Memory Utilization
- Monitoring Module Upgrade and Optimization in Guangzhou and Shanghai Regions
- Monitoring Module Upgrade
- Parameter Template and Instance Purchase Process Optimization
- Binlog Will Take up Disk Space
- User Tutorial
- Product Introduction
- Tencent Kernel TXSQL
- Overview
- Kernel Version Release Notes
- Functionality Features
- Performance Features
- Security Features
- Stability Features
- TXRocks Engine
- Purchase Guide
- Billing Overview
- Selection Guide
- Purchase Methods
- Renewal
- Payment Overdue
- Refund
- Pay-as-You-Go to Monthly Subscription
- Instance Adjustment Fee
- Backup Space Billing
- Database Audit Billing Overview
- Commercial Billing and Activity Description for Database Proxy
- Description of the Database Proxy Billing Cycle
- Viewing Bills
- Getting Started
- Database Audit
- MySQL Cluster Edition
- Operation Guide
- Use Limits
- Operation Overview
- Instance Management and Maintenance
- Instance Upgrade
- CPU Elastic Expansion
- Read-Only/Disaster Recovery Instances
- Database Proxy
- Account Management
- Database Management Center (DMC)
- Parameter Configuration
- Network and Security
- Backup and Rollback
- Data Migration
- Monitoring and Alarms
- Operation Logs
- Tag
- Practical Tutorial
- Usage Specifications of TencentDB for MySQL
- Configuring Automatic Application Reconnection
- Impact of Modifying MySQL Source Instance Parameters
- Limits on Automatic Conversion from MyISAM to InnoDB
- Creating VPCs for TencentDB for MySQL
- Enhancing Business Load Capacity with TencentDB for MySQL
- Setting up 2-Region-3-DC Disaster Recovery Architecture
- Improving TencentDB for MySQL Performance with Read/Write Separation
- Migrating Data from InnoDB to RocksDB with DTS
- Building LAMP Stack for Web Application
- Building Drupal Website
- Building All-Scenario High-Availability Architecture
- Calling MySQL APIs in Python
- White Paper
- Troubleshooting
- API Documentation
- History
- Introduction
- API Category
- Data Import APIs
- Rollback APIs
- Parameter APIs
- Making API Requests
- Instance APIs
- StopCpuExpand
- StartCpuExpand
- DescribeCpuExpandStrategy
- AddTimeWindow
- BalanceRoGroupLoad
- CloseWanService
- CreateRoInstanceIp
- DeleteTimeWindow
- DescribeCdbZoneConfig
- DescribeDBFeatures
- DescribeDBInstanceCharset
- DescribeDBInstanceConfig
- DescribeDBInstanceGTID
- DescribeDBInstanceInfo
- DescribeDBInstanceRebootTime
- DescribeDBSwitchRecords
- DescribeRoGroups
- DescribeRoMinScale
- DescribeTagsOfInstanceIds
- DescribeTimeWindow
- IsolateDBInstance
- ModifyAutoRenewFlag
- ModifyDBInstanceName
- ModifyDBInstanceProject
- ModifyDBInstanceVipVport
- ModifyInstanceTag
- ModifyNameOrDescByDpId
- ModifyRoGroupInfo
- ModifyTimeWindow
- OfflineIsolatedInstances
- OpenDBInstanceEncryption
- OpenDBInstanceGTID
- OpenWanService
- ReleaseIsolatedDBInstances
- RenewDBInstance
- RestartDBInstances
- StartReplication
- StopReplication
- SwitchDBInstanceMasterSlave
- SwitchDrInstanceToMaster
- SwitchForUpgrade
- UpgradeDBInstanceEngineVersion
- CreateDBInstance
- CreateDBInstanceHour
- DescribeDBInstances
- UpgradeDBInstance
- DescribeDBZoneConfig
- CreateDeployGroup
- DeleteDeployGroups
- DescribeDeployGroupList
- Database Proxy APIs
- AdjustCdbProxy
- AdjustCdbProxyAddress
- CloseCDBProxy
- CloseCdbProxyAddress
- CreateCdbProxy
- CreateCdbProxyAddress
- DescribeCdbProxyInfo
- DescribeProxyCustomConf
- DescribeProxySupportParam
- ModifyCdbProxyAddressDesc
- ModifyCdbProxyAddressVipAndVPort
- ModifyCdbProxyParam
- ReloadBalanceProxyNode
- SwitchCDBProxy
- UpgradeCDBProxyVersion
- Database Audit APIs
- Security APIs
- Task APIs
- Account APIs
- Backup APIs
- CreateBackup
- DeleteBackup
- DescribeBackupDownloadRestriction
- DescribeBackupOverview
- DescribeBackupSummaries
- DescribeBinlogBackupOverview
- DescribeDataBackupOverview
- DescribeLocalBinlogConfig
- DescribeRemoteBackupConfig
- DescribeSlowLogs
- ModifyBackupDownloadRestriction
- ModifyLocalBinlogConfig
- ModifyRemoteBackupConfig
- DescribeBackups
- DescribeBackupConfig
- DescribeBackupDecryptionKey
- DescribeBackupEncryptionStatus
- DescribeBinlogs
- ModifyBackupConfig
- ModifyBackupEncryptionStatus
- Database APIs
- Monitoring APIs
- Log-related API
- Data Types
- Error Codes
- FAQs
- Service Agreement
- Reference
- Glossary
- Contact Us
- Preset Plugin List
- Release Notes and Announcements
- Release Notes
- Announcements
- Announcement on the Rule-Based Audit Feature for Database Audit
- Announcement on Some APIs with CAM Authentication Integrated
- Announcement on Some APIs with CAM Authentication Integrated
- Notice on Elimination of Some Indicators in Event Alarms
- Commercial Billing for Database Proxy
- TencentDB for MySQL Audit Upgrade
- Added Authentication APIs
- API Authentication Upgrade
- TencentDB for MySQL API 2.0 Discontinuation
- Monitoring Module Upgrade in Shanghai Region
- Monitoring Metric Optimization
- Network Architecture Upgrade
- Change of APIs for Querying the Specifications of Purchasable Database Instances
- Replacement of Certain Old Database Proxy APIs
- Added Advanced Monitoring Metrics
- Change of Calculation Formula for Memory Utilization
- Monitoring Module Upgrade and Optimization in Guangzhou and Shanghai Regions
- Monitoring Module Upgrade
- Parameter Template and Instance Purchase Process Optimization
- Binlog Will Take up Disk Space
- User Tutorial
- Product Introduction
- Tencent Kernel TXSQL
- Overview
- Kernel Version Release Notes
- Functionality Features
- Performance Features
- Security Features
- Stability Features
- TXRocks Engine
- Purchase Guide
- Billing Overview
- Selection Guide
- Purchase Methods
- Renewal
- Payment Overdue
- Refund
- Pay-as-You-Go to Monthly Subscription
- Instance Adjustment Fee
- Backup Space Billing
- Database Audit Billing Overview
- Commercial Billing and Activity Description for Database Proxy
- Description of the Database Proxy Billing Cycle
- Viewing Bills
- Getting Started
- Database Audit
- MySQL Cluster Edition
- Operation Guide
- Use Limits
- Operation Overview
- Instance Management and Maintenance
- Instance Upgrade
- CPU Elastic Expansion
- Read-Only/Disaster Recovery Instances
- Database Proxy
- Account Management
- Database Management Center (DMC)
- Parameter Configuration
- Network and Security
- Backup and Rollback
- Data Migration
- Monitoring and Alarms
- Operation Logs
- Tag
- Practical Tutorial
- Usage Specifications of TencentDB for MySQL
- Configuring Automatic Application Reconnection
- Impact of Modifying MySQL Source Instance Parameters
- Limits on Automatic Conversion from MyISAM to InnoDB
- Creating VPCs for TencentDB for MySQL
- Enhancing Business Load Capacity with TencentDB for MySQL
- Setting up 2-Region-3-DC Disaster Recovery Architecture
- Improving TencentDB for MySQL Performance with Read/Write Separation
- Migrating Data from InnoDB to RocksDB with DTS
- Building LAMP Stack for Web Application
- Building Drupal Website
- Building All-Scenario High-Availability Architecture
- Calling MySQL APIs in Python
- White Paper
- Troubleshooting
- API Documentation
- History
- Introduction
- API Category
- Data Import APIs
- Rollback APIs
- Parameter APIs
- Making API Requests
- Instance APIs
- StopCpuExpand
- StartCpuExpand
- DescribeCpuExpandStrategy
- AddTimeWindow
- BalanceRoGroupLoad
- CloseWanService
- CreateRoInstanceIp
- DeleteTimeWindow
- DescribeCdbZoneConfig
- DescribeDBFeatures
- DescribeDBInstanceCharset
- DescribeDBInstanceConfig
- DescribeDBInstanceGTID
- DescribeDBInstanceInfo
- DescribeDBInstanceRebootTime
- DescribeDBSwitchRecords
- DescribeRoGroups
- DescribeRoMinScale
- DescribeTagsOfInstanceIds
- DescribeTimeWindow
- IsolateDBInstance
- ModifyAutoRenewFlag
- ModifyDBInstanceName
- ModifyDBInstanceProject
- ModifyDBInstanceVipVport
- ModifyInstanceTag
- ModifyNameOrDescByDpId
- ModifyRoGroupInfo
- ModifyTimeWindow
- OfflineIsolatedInstances
- OpenDBInstanceEncryption
- OpenDBInstanceGTID
- OpenWanService
- ReleaseIsolatedDBInstances
- RenewDBInstance
- RestartDBInstances
- StartReplication
- StopReplication
- SwitchDBInstanceMasterSlave
- SwitchDrInstanceToMaster
- SwitchForUpgrade
- UpgradeDBInstanceEngineVersion
- CreateDBInstance
- CreateDBInstanceHour
- DescribeDBInstances
- UpgradeDBInstance
- DescribeDBZoneConfig
- CreateDeployGroup
- DeleteDeployGroups
- DescribeDeployGroupList
- Database Proxy APIs
- AdjustCdbProxy
- AdjustCdbProxyAddress
- CloseCDBProxy
- CloseCdbProxyAddress
- CreateCdbProxy
- CreateCdbProxyAddress
- DescribeCdbProxyInfo
- DescribeProxyCustomConf
- DescribeProxySupportParam
- ModifyCdbProxyAddressDesc
- ModifyCdbProxyAddressVipAndVPort
- ModifyCdbProxyParam
- ReloadBalanceProxyNode
- SwitchCDBProxy
- UpgradeCDBProxyVersion
- Database Audit APIs
- Security APIs
- Task APIs
- Account APIs
- Backup APIs
- CreateBackup
- DeleteBackup
- DescribeBackupDownloadRestriction
- DescribeBackupOverview
- DescribeBackupSummaries
- DescribeBinlogBackupOverview
- DescribeDataBackupOverview
- DescribeLocalBinlogConfig
- DescribeRemoteBackupConfig
- DescribeSlowLogs
- ModifyBackupDownloadRestriction
- ModifyLocalBinlogConfig
- ModifyRemoteBackupConfig
- DescribeBackups
- DescribeBackupConfig
- DescribeBackupDecryptionKey
- DescribeBackupEncryptionStatus
- DescribeBinlogs
- ModifyBackupConfig
- ModifyBackupEncryptionStatus
- Database APIs
- Monitoring APIs
- Log-related API
- Data Types
- Error Codes
- FAQs
- Service Agreement
- Reference
- Glossary
- Contact Us
- Preset Plugin List
TencentDB 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.
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