parallel_min_scan_time_threshold

Description

parallel_min_scan_time_threshold specifies the minimum execution time for evaluating a base table scan before parallel processing is enabled. This parameter is used in the Auto DOP strategy to calculate the degree of parallelism. When the evaluation execution time exceeds this threshold, parallel processing is enabled, and the threshold is used to calculate an appropriate degree of parallelism.

Privilege requirements

• Query variables

  • Global level

    sys tenants and all user tenants can execute the SHOW VARIABLES statement or query the SYS.TENANT_VIRTUAL_GLOBAL_VARIABLE view (Oracle mode) or the information_schema.GLOBAL_VARIABLES view (MySQL mode) to obtain the value of a global system variable.

  • Session level

    sys tenants and all user tenants can execute the SHOW VARIABLES statement or query the SYS.TENANT_VIRTUAL_SESSION_VARIABLE view (Oracle mode) or the information_schema.SESSION_VARIABLES view (MySQL mode) to obtain the value of a session system variable.

• Modify variables

  • Global level

    • sys tenants can directly modify the value of a global system variable.

    • MySQL user tenants must have the SUPER or ALTER SYSTEM privilege to modify the value of a global system variable.

    • Oracle user tenants must have the ALTER SYSTEM privilege to modify the value of a global system variable.

  • Session level

    sys tenants and all user tenants can directly modify the value of a session system variable of their own tenant.

Attributes

Examples

Set the minimum execution time for evaluating a base table scan before parallel processing is enabled to 100 ms. 100 ms is the value of the parallel_min_scan_time_threshold parameter.

• Session level

  obclient> SET parallel_min_scan_time_threshold = 100;
  

• Global level

  obclient> SET GLOBAL parallel_min_scan_time_threshold = 100;