The COLUMNS_EXTENSIONS table (available as of
      MySQL 8.0.21) provides information about column attributes defined
      for primary and secondary storage engines.
        The COLUMNS_EXTENSIONS table is
        reserved for future use.
      The COLUMNS_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. 
- COLUMN_NAME- The name of the column. 
- ENGINE_ATTRIBUTE- Column attributes defined for the primary storage engine. Reserved for future use. 
- SECONDARY_ENGINE_ATTRIBUTE- Column attributes defined for the secondary storage engine. Reserved for future use.