public boolean readField(int fieldIndex) throws IOException {
    throw new RuntimeException("Not supported");
  }
Constructor.

When useExternalBuffer is specified true and readNextField reads a string/char/varchar/binary
field, it will request an external buffer to receive the data of format conversion.

if (deserializeRead.readNextField()) {
  if (deserializeRead.currentExternalBufferNeeded) {
    &lt;Ensure external buffer is as least deserializeRead.currentExternalBufferNeededLen bytes&gt;
    deserializeRead.copyToExternalBuffer(externalBuffer, externalBufferStart);
  } else {
    &lt;Otherwise, field data is available in the currentBytes, currentBytesStart, and
     currentBytesLength of deserializeRead&gt;
  }

@param typeInfos
@param dataTypePhysicalVariations
                           Specify for each corresponding TypeInfo a read variation. Can be
                           null.  dataTypePhysicalVariation.NONE is then assumed.
@param useExternalBuffer   Specify true when the caller is prepared to provide a bytes buffer
                           to receive a string/char/varchar/binary field that needs format
                           conversion.
serde/src/java/org/apache/hadoop/hive/serde2/fast/DeserializeRead.java