See attachment for proposed fix. It always adds _delete_list to Par2Backend. And _delete_list fallbacks to _delete calls if wrapped backend has no _delet_list.
I've compared it on very small 18-volume backup of duplicity source code (--volsize=2 --no-encryption).
Full backups: 2 (deleting one of them)
before: 40.927 secs
fixed : 36.076 secs
Full backups: 25 (deleting one of them)
before: 1:55.27 total
fixed : 50.213 total
See attachment for proposed fix. It always adds _delete_list to Par2Backend. And _delete_list fallbacks to _delete calls if wrapped backend has no _delet_list.
I've compared it on very small 18-volume backup of duplicity source code (--volsize=2 --no-encryption).
Full backups: 2 (deleting one of them)
before: 40.927 secs
fixed : 36.076 secs
Full backups: 25 (deleting one of them)
before: 1:55.27 total
fixed : 50.213 total