code: private AttributeValue mapColumnValue(String storeName, DColumn col) {
          AttributeValue attrValue = new AttributeValue();
          if (!DBService.isSystemTable(storeName)) {
              if (col.getRawValue().length == 0) {
                  attrValue.setS(DynamoDBService.NULL_COLUMN_MARKER);
              } else {
                  attrValue.setB(ByteBuffer.wrap(col.getRawValue()));
              }
          } else {
              String strValue = col.getValue();
              if (strValue.length() == 0) {
                  strValue = DynamoDBService.NULL_COLUMN_MARKER;
              }
              attrValue.setS(strValue);
          }
          return attrValue;
      }
docs: Create the appropriate AttributeValue for the given column value type and length.