public TSStatus unsetTTL(SetTTLPlan plan) {
    TSStatus status;
    lock.writeLock().lock();
    try {
      status = ttlCache.unsetTTL(plan.getPathPattern());
      if (status.code == TSStatusCode.SUCCESS_STATUS.getStatusCode() && plan.isDataBase()) {
        // unset ttl to path.**
        status =
            ttlCache.unsetTTL(
                new PartialPath(plan.getPathPattern())
                    .concatNode(IoTDBConstant.MULTI_LEVEL_PATH_WILDCARD)
                    .getNodes());
      }
    } finally {
      lock.writeLock().unlock();
    }
    return status;
  }
Only used for upgrading from database level ttl to device level ttl.
iotdb-core/confignode/src/main/java/org/apache/iotdb/confignode/persistence/TTLInfo.java