docs: public Optional<ShardingEncryptor> getShardingEncryptor(final String logicTableName, final String columnName) {
          return Collections2.filter(columns, new Predicate<ColumnNode>() {
              
              @Override
              public boolean apply(final ColumnNode input) {
                  return input.equals(new ColumnNode(logicTableName, columnName));
              }
          }).isEmpty() ? Optional.<ShardingEncryptor>absent() : Optional.of(shardingEncryptor);
      }