When using backup with lock-ddl=REDUCED and backing up an external data directory, the process does not properly manage general tablespaces. Specifically, when processing delete or rename DDL statements, the backup incorrectly treats the directory containing the general tablespace as a schema. For example, if the general tablespace is located at:

ext_dir/ext_subdir/gen_tab.ibd

After handling a delete DDL, it creates the following file:

backup/ext_subdir/space_id.del

However, it should be created as:

backup/space_id.del (without the subdirectory).