parallel_min_scan_time_threshold

Description

parallel_min_scan_time_threshold is a parameter used in the Auto DOP strategy to calculate the parallelism. It specifies the minimum evaluation execution time for parallel processing of base table scans. When the evaluation execution time for a base table scan exceeds this threshold, parallel processing is initiated, and the parallelism is calculated based on this value.

Privilege requirements

• Query variables

  • Global level

    The sys tenant and all user tenants can use the SHOW VARIABLES statement or the SYS.TENANT_VIRTUAL_GLOBAL_VARIABLE view (Oracle-compatible mode) and the information_schema.GLOBAL_VARIABLES view (MySQL-compatible mode) to view the values of global system variables.

  • Session level

    The sys tenant and all user tenants can use the SHOW VARIABLES statement or the SYS.TENANT_VIRTUAL_SESSION_VARIABLE view (Oracle-compatible mode) and the information_schema.SESSION_VARIABLES view (MySQL-compatible mode) to view the values of session system variables.

• Modify variables

  • Global level

    • The sys tenant can directly modify the values of global system variables.

    • MySQL user tenants need to have the SUPER or ALTER SYSTEM privilege to modify the values of global system variables.

    • Oracle user tenants need to have the ALTER SYSTEM privilege to modify the values of global system variables.

  • Session level

    The sys tenant and all user tenants can directly modify the values of session system variables.

Attributes

Examples

Set the minimum evaluation execution time for parallel processing of base table scans to 100 ms.

• Session level

  obclient> SET parallel_min_scan_time_threshold = 100;
  

• Global level

  obclient> SET GLOBAL parallel_min_scan_time_threshold = 100;