MySQL 8.4 Reference Manual Including MySQL NDB Cluster 8.4
SET RESOURCE GROUPgroup_name[FORthread_id[,thread_id] ...]
        SET RESOURCE GROUP is used for
        resource group management (see
        Section 7.1.16, “Resource Groups”). This statement assigns
        threads to a resource group. It requires the
        RESOURCE_GROUP_ADMIN or
        RESOURCE_GROUP_USER privilege.
      
        group_name identifies which resource
        group to be assigned. Any thread_id
        values indicate threads to assign to the group. Thread IDs can
        be determined from the Performance Schema
        threads table. If the resource
        group or any named thread ID does not exist, an error occurs.
      
        With no FOR clause, the statement assigns the
        current thread for the session to the resource group.
      
        With a FOR clause that names thread IDs, the
        statement assigns those threads to the resource group.
      
For attempts to assign a system thread to a user resource group or a user thread to a system resource group, a warning occurs.
Examples:
Assign the current session thread to a group:
SET RESOURCE GROUP rg1;
Assign the named threads to a group:
SET RESOURCE GROUP rg2 FOR 14, 78, 4;
        Resource group management is local to the server on which it
        occurs. SET RESOURCE GROUP
        statements are not written to the binary log and are not
        replicated.
      
        An alternative to SET RESOURCE
        GROUP is the
        RESOURCE_GROUP optimizer hint,
        which assigns individual statements to a resource group. See
        Section 10.9.3, “Optimizer Hints”.