public class DataConverter {

      ...

      case Types.NUMERIC:
        if (mapNumerics) {
          int precision = metadata.getPrecision(col);
          if (precision < 19) {
            Schema schema;
            if (metadata.getScale(col) == 0) { // integer
              if (precision > 9) {
                schema = (optional) ? Schema.OPTIONAL_INT64_SCHEMA :
                        Schema.INT64_SCHEMA;
              } else if (precision > 4) {
                schema = (optional) ? Schema.OPTIONAL_INT32_SCHEMA :
                        Schema.INT32_SCHEMA;
              } else if (precision > 2) {
                schema = (optional) ? Schema.OPTIONAL_INT16_SCHEMA :
                        Schema.INT16_SCHEMA;
              } else {
                schema = (optional) ? Schema.OPTIONAL_INT8_SCHEMA :
                        Schema.INT8_SCHEMA;
              }
            } else { // double
              schema = (optional) ? Schema.OPTIONAL_FLOAT64_SCHEMA :
                          Schema.FLOAT64_SCHEMA;
            }

            builder.field(fieldName, schema);
            break;
          }
        }

      ...

      case Types.NUMERIC:
        if (mapNumerics) {
          ResultSetMetaData metadata = resultSet.getMetaData();
          int precision = metadata.getPrecision(col);
          if (precision < 19) {
            if (metadata.getScale(col) == 0) { // integer
              if (precision > 9) {
                colValue = resultSet.getLong(col);
              } else if (precision > 4) {
                colValue = resultSet.getInt(col);
              } else if (precision > 2) {
                colValue = resultSet.getShort(col);
              } else {
                colValue = resultSet.getByte(col);
              }
              break;
            } else { // double
              colValue = resultSet.getDouble(col);
              break;
            }
          }
        }

      ...

}