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DocumentationTDSQL-C for MySQLKernel FeaturesPerformance FeaturesOptimization of Plan Caching Point Query
Optimization of Plan Caching Point Query
Last updated: 2024-04-25 11:10:02
Overview
In TDSQL-C for MySQL, SQL statement execution is divided into four stages: parsing, preparation, optimization, and execution. The execution plan cache feature is only available for prepared statements. After the feature is enabled, the first three stages will be skipped when executing a prepared statement, greatly boosting query performance.
Supported Versions
TDSQL-C for MySQL 8.0 (kernel version 3.1.10) or later.
Use Cases
This feature is mainly used to improve the query performance when executing many online short point queries with prepared statements. The specific extent of performance improvement depends on the online business.
Use Limits
You can use the
cdb_plan_cache parameter to enable or disable the execution plan cache and the cdb_plan_cache_stats parameter to query information about cache hits.Parameter | Status | Type | Default Value | Valid Values | Description |
cdb_plan_cache | yes | bool | false | true/false | Whether to enable the feature. Only accounts with the feature permission can use the parameter. |
Note:
Currently, you cannot directly modify the values of the above parameter. If needed, submit a ticket for assistance.
Upon enabling the
cdb_plan_cache_stats parameter, one can then view related data through the show cdb_plan_cache_stat command.You can run the
show cdb_plan_cache_stat command to query information about execution plan cache hits. The command will return the following fields:Field | Description |
sql | A SQL statement with the question mark (?) which represents that the execution plan of this statement has been cached. |
mode | SQL cache mode. Currently, only the prepare mode is supported. |
hit | Number of hits for this session |
Note：
When the
cdb_plan_cache_stats switch is enabled, it essentially functions as an information record, which will have an impact on performance.Was this page helpful?
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