ENABLE_OPTIMIZER_ROWGOAL

Description

ENABLE_OPTIMIZER_ROWGOAL specifies whether to consider the row goal (such as the LIMIT operator) when the optimizer estimates the cardinality.

Privilege requirements

• Global level

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

  • Session level

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

• Modify variables

  • Global level

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

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

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

  • Session level

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

Attributes

Examples

Execute the following command to enable the row goal for cardinality estimation.

• Global level

  obclient> SET GLOBAL enable_optimizer_rowgoal=ON;
  

• Session level

  obclient> SET enable_optimizer_rowgoal=ON;