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- Release Notes and Announcements
- Release Notes
- Announcements
- 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
- Getting Started
- Database Audit
- 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
- Best Practices
- 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
- Making API Requests
- Instance APIs
- StopCpuExpand
- StartCpuExpand
- DescribeCpuExpandStrategy
- AddTimeWindow
- BalanceRoGroupLoad
- CloseWanService
- CreateDBInstance
- CreateDBInstanceHour
- CreateRoInstanceIp
- DeleteTimeWindow
- DescribeCdbZoneConfig
- DescribeDBFeatures
- DescribeDBInstanceCharset
- DescribeDBInstanceConfig
- DescribeDBInstanceGTID
- DescribeDBInstanceInfo
- DescribeDBInstanceRebootTime
- DescribeDBSwitchRecords
- DescribeRoGroups
- DescribeRoMinScale
- DescribeTagsOfInstanceIds
- DescribeTimeWindow
- InitDBInstances
- IsolateDBInstance
- ModifyAutoRenewFlag
- ModifyDBInstanceName
- ModifyDBInstanceProject
- ModifyDBInstanceVipVport
- ModifyInstanceTag
- ModifyRoGroupInfo
- ModifyTimeWindow
- OfflineIsolatedInstances
- OpenDBInstanceEncryption
- OpenDBInstanceGTID
- OpenWanService
- ReleaseIsolatedDBInstances
- RenewDBInstance
- RestartDBInstances
- StartReplication
- StopReplication
- SwitchDBInstanceMasterSlave
- SwitchDrInstanceToMaster
- SwitchForUpgrade
- UpgradeDBInstance
- UpgradeDBInstanceEngineVersion
- DescribeDBInstances
- DescribeDBZoneConfig
- CreateDeployGroup
- DeleteDeployGroups
- DescribeDeployGroupList
- ModifyNameOrDescByDpId
- Data Import APIs
- Database Proxy APIs
- AdjustCdbProxy
- AdjustCdbProxyAddress
- CloseCdbProxyAddress
- CreateCdbProxy
- CreateCdbProxyAddress
- DescribeCdbProxyInfo
- DescribeProxySupportParam
- ModifyCdbProxyAddressDesc
- ModifyCdbProxyAddressVipAndVPort
- ModifyCdbProxyParam
- CloseCDBProxy
- DescribeProxyCustomConf
- ReloadBalanceProxyNode
- SwitchCDBProxy
- UpgradeCDBProxyVersion
- Database Audit APIs
- Security APIs
- Task APIs
- Account APIs
- Backup APIs
- DescribeBackupDecryptionKey
- CreateBackup
- DeleteBackup
- DescribeBackupDownloadRestriction
- DescribeBackupEncryptionStatus
- DescribeBackupOverview
- DescribeBackupSummaries
- DescribeBinlogBackupOverview
- DescribeDataBackupOverview
- DescribeLocalBinlogConfig
- DescribeRemoteBackupConfig
- DescribeSlowLogs
- ModifyBackupDownloadRestriction
- ModifyBackupEncryptionStatus
- ModifyLocalBinlogConfig
- ModifyRemoteBackupConfig
- DescribeBackups
- DescribeBackupConfig
- ModifyBackupConfig
- DescribeBinlogs
- Rollback APIs
- Parameter APIs
- Database APIs
- Monitoring APIs
- Log-related API
- Data Types
- Error Codes
- FAQs
- Service Agreement
- Reference
- Glossary
- Contact Us
- Preset Plugin List
Supported Statement Scenarios and Restricted Scenarios
Last updated: 2023-08-10 18:02:02
This document describes the supported statement scenarios and restricted scenarios of the parallel query.
Supported statement scenarios
TencentDB for MySQL has implemented the parallel query feature for SQL statements with the following characteristics, with more to come.
- Single-table scan: Full-table scan, index scan, index range scan, and index REF query in ascending or descending order are supported.
- Multi-table join: The nested-loop join (NLJ) algorithm as well as semi join, anti join, and outer join are supported.
- Subquery: Parallel query is supported for derived tables.
- Data type: Different data types can be queried, such as integer, string, floating point, time, and overflow (with a runtime size limit).
- There are no restrictions on common operators and functions.
- COUNT, SUM, AVG, MIN, and MAX aggregate functions are supported.
- UNION and UNION ALL queries are supported.
- Traditional (default), JSON, and tree EXPLAIN formats are supported.
Restricted scenarios
The parallel query feature of TencentDB for MySQL is not supported in the following scenarios.
| Restriction | Description |
|---|---|
| Statement compatibility restriction | Parallel query is not supported for non-query statements, including `INSERT ... SELECT` and `REPLACE ... SELECT`. |
| Parallel query is not supported for statements in a stored program. | |
| Parallel query is not supported for prepared statements. | |
| Parallel query is not supported for statements in serial isolation-level transactions. | |
| Parallel query is not supported for locking reads, such as `SELECT FOR UPDATE` and `SELECT ... FOR SHARE`. | |
| Parallel query is not supported for CTEs. | |
| Table/Index compatibility restriction | Parallel query is not supported for system, temp, and non-InnoDB tables. |
| Parallel query is not supported for space index. | |
| Parallel query is not supported for full-text index. | |
| Parallel query is not supported for partitioned tables. | |
| Parallel query is not supported for tables in `index_merge` scan mode. | |
| Expression/Field compatibility restriction | Parallel query is not supported for tables containing generated columns or BLOB, TEXT, JSON, BIT, and GEOMETRY fields. |
| Parallel query is not supported for aggregate functions of the BIT_AND, BIT_OR, or BIT_XOR type. | |
| Parallel query is not supported for DISTINCT aggregations, such as SUM(DISTINCT) and COUNT(DISTINCT). | |
| Parallel query is not supported for GIS functions such as SP_WITHIN_FUNC and ST_DISTANCE. | |
| Parallel query is not supported for custom functions. | |
| Parallel query is not supported for JSON functions such as JSON_LENGTH, JSON_TYPE, and JSON_ARRAYAGG. | |
| Parallel query is not supported for XML functions such as XML_STR. | |
| Parallel query is not supported for user-lock functions such as IS_FREE_LOCK, IS_USED_LOCK, RELEASE_LOCK, RELEASE_ALL_LOCKS, and GET_LOCK. | |
| Parallel query is not supported for SLEEP, RANDOM, GROUP_CONCAT, SET_USER_VAR, and WEIGHT_STRING functions. | |
| Parallel query is not supported for certain statistical functions such as STD, STDDEV, STDDEV_POP, VARIANCE, VAR_POP, and VAR_SAMP. | |
| Parallel query is not supported for subqueries. | |
| Parallel query is not supported for window functions. | |
| Parallel query is not supported for ROLLUP. |
Besides the above examples in Supported statement scenarios, you can also check the parallel query execution plan and thread working status to see whether a statement can be queried parallelly. For more information, see Viewing Parallel Query.
Yes
No
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