fix restore compat issue from low-version observer backup

src/rootserver/restore/ob_restore_util.cpp

@@ -691,13 +691,21 @@ int ObRestoreUtil::inner_fill_compat_backup_path(
     LOG_WARN("failed to get backup path list", KR(ret), K(uri_list));
   } else if (OB_FAIL(job.multi_restore_path_list_.set(backup_set_list, backup_piece_list))) {
     LOG_WARN("failed to set mutli restore path list", KR(ret));
-  } else if (OB_FAIL(ObMultiBackupDestUtil::check_can_restore_by_set_or_piece(backup_set_list, backup_piece_list))) {
+  } else {
+    // history reason, before 2277, the inc backup set is nested in full backup set
+    // so if the backup set list is empty and backup piece list is not empty
+    // it is compat path which the backup is from 2276 or before
+    const bool is_compat_path = backup_set_list.empty() && !backup_piece_list.empty();
+    if (!is_compat_path) {
+      if (OB_FAIL(ObMultiBackupDestUtil::check_can_restore_by_set_or_piece(backup_set_list, backup_piece_list))) {
         if (OB_BACKUP_FILE_NOT_EXIST == ret) {
           LOG_WARN("the backup file is missing and cannot be restored", K(ret));
+        }
       } else {
         LOG_WARN("failed to check can be restored", KR(ret));
       }
     }
+  }
   return ret;
 }