ob_compatibility_control

Description

MySQL 5.7 and 8.0 have conflicting behaviors in some scenarios. For example, REPLACE('abd','',null) returns different results in MySQL 5.7 and 8.0. ob_compatibility_control specifies whether to follow MySQL 5.7 or MySQL 8.0 behavior when you create a tenant and a compatibility conflict arises. This variable cannot be modified after the tenant is created. In either compatibility mode, you can use the superset of MySQL 5.7 and 8.0 features that are free of compatibility conflicts.

Privilege requirements

• Query variables

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

• Modify variables

  After a tenant is created, you cannot modify this variable by executing an SQL statement.

Attributes

Usage notes

• When you upgrade a tenant that does not have this variable to a version that has this variable, the variable takes the default value MYSQL5.7. When you create a new tenant, you can specify the compatibility mode.

• For features that were already implemented following MySQL 8.0 behavior in earlier versions, if ob_compatibility_version < 4.2.3, these features remain compatible with MySQL 8.0 regardless of the value of ob_compatibility_control.

Examples

Specify the compatibility mode as MySQL 5.7 when you create a tenant.

obclient> create tenant tenant_m57 zone_list=('z1'),primary_zone='z1',resource_pool_list=('pool1') set ob_compatibility_mode='mysql',ob_compatibility_control='MYSQL5.7',ob_tcp_invited_nodes='%';

References

• ob_compatibility_version
• V$OB_COMPATIBILITY_CONTROL