MySQL 8.4 Reference Manual Including MySQL NDB Cluster 8.4
      The TABLES_EXTENSIONS table provides
      information about table attributes defined for primary and
      secondary storage engines.
    
        The TABLES_EXTENSIONS table is
        reserved for future use.
      
      The TABLES_EXTENSIONS table has these
      columns:
    
          TABLE_CATALOG
        
          The name of the catalog to which the table belongs. This value
          is always def.
        
          TABLE_SCHEMA
        
The name of the schema (database) to which the table belongs.
          TABLE_NAME
        
The name of the table.
          ENGINE_ATTRIBUTE
        
Table attributes defined for the primary storage engine. Reserved for future use.
          SECONDARY_ENGINE_ATTRIBUTE
        
Table attributes defined for the secondary storage engine. Reserved for future use.