query_rewrite_enabled

Description

The query_rewrite_enabled variable specifies whether to enable materialized view-based query rewriting.

Privilege requirements

• Query variables

  • Global level

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

  • Session level

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

• Modify variables

  • Set the variable at the global level

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

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

    • For V4.x, Oracle users of user tenants need the ALTER SYSTEM privilege to modify the values of global system variables starting from V4.2.0.

  • Set the variable at the session level

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

Attributes

Examples

The following examples show how to enable materialized view-based query rewriting.

• Set the variable at the session level

  obclient> SET  query_rewrite_enabled= true;
  

• Set the variable at the global level

  obclient> SET GLOBAL  query_rewrite_enabled= true;
  

References

• query_rewrite_integrity
• Overview of materialized views