code: @Override
      public void tag(final String tagString) throws DatabaseException {
          Database database = getDatabase();
          Executor executor = ExecutorService.getInstance().getExecutor(database);
          int totalRows = ExecutorService.getInstance().getExecutor(database).queryForInt(new
              SelectFromDatabaseChangeLogStatement(new ColumnConfig().setName("COUNT(*)", true)));
          if (totalRows == 0) {
              ChangeSet emptyChangeSet = new ChangeSet(String.valueOf(new Date().getTime()), "liquibase",
                  false,false, "liquibase-internal", null, null,
                  getDatabase().getObjectQuotingStrategy(), null);
              this.setExecType(emptyChangeSet, ChangeSet.ExecType.EXECUTED);
          }
  
          executor.execute(new TagDatabaseStatement(tagString));
          getDatabase().commit();
  
          if (this.ranChangeSetList != null) {
              ranChangeSetList.get(ranChangeSetList.size() - 1).setTag(tagString);
          }
      }
docs: Tags the database changelog with the given string.