ob_udf_cost_factor

Overview

The ob_udf_cost_factor parameter specifies the cost factor for UDF predicates.

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 (in Oracle-compatible mode) and the information_schema.GLOBAL_VARIABLES view (in MySQL-compatible mode), to view the values of global system variables.

  • Session level

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

• Modify variables

  • Global effective

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

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

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

  • Session expiration

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

Attributes

Usage instructions

This variable is used to adjust the cost coefficient of a UDF predicate, which affects the optimizer's decision on the execution order of predicates. The cost coefficient represents the actual runtime cost of a UDF predicate when processing each record. It can be configured according to the specific situation of the UDF predicate. Generally, the default value of 100 is sufficient.

Configuration example

Set the cost coefficient of the UDF predicate to 100000.

• Effective globally

  obclient> SET GLOBAL ob_udf_cost_factor = 100000;
  

• Session expiration

  obclient> SET ob_udf_cost_factor = 100000;