code: public final double getDouble(int columnIndex) {
          validateColumnType(columnIndex, VoltType.FLOAT);
          final double value = m_buffer.getDouble(getOffset(columnIndex));
          m_wasNull = (value <= VoltType.NULL_FLOAT); // see value.h
          return value;
      }
docs: Retrieve the <tt>double</tt> value stored in the column specified by index.
  Looking at the return value is not a reliable way to check if the value
  is <tt>null</tt>. Use {@link #wasNull()} instead.
  @param columnIndex Index of the column
  @return <tt>double</tt> value stored in the specified column
  @see #wasNull()