func (t Transition) MarshalXML(enc *xml.Encoder, start xml.StartElement) error {
	if !t.set {
		return nil
	}
	type transitionWrapper Transition
	return enc.EncodeElement(transitionWrapper(t), start)
}

// UnmarshalXML decodes transition field from the XML form.
func (t *Transition) UnmarshalXML(d *xml.Decoder, startElement xml.StartElement) error {
	type transitionWrapper Transition

	unmarshaled bool
}

// IsEmpty - returns whether reader args is empty or not.
func (args *ReaderArgs) IsEmpty() bool {
	return !args.unmarshaled
}

// UnmarshalXML - decodes XML data.
func (args *ReaderArgs) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
	// Make subtype to avoid recursive UnmarshalXML().
	type subReaderArgs ReaderArgs
	parsedArgs := subReaderArgs{}

// MarshalXML encodes delete marker boolean into an XML form.
func (b Boolean) MarshalXML(e *xml.Encoder, startElement xml.StartElement) error {
	if !b.set {
		return nil
	}
	return e.EncodeElement(b.val, startElement)
}

// UnmarshalXML decodes delete marker boolean from the XML form.
func (b *Boolean) UnmarshalXML(d *xml.Decoder, startElement xml.StartElement) error {
	var exp bool
	err := d.DecodeElement(&exp, &startElement)

func (filter FilterRule) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
	if filter.isEmpty() {
		return nil
	}
	type filterRuleWrapper FilterRule
	return e.EncodeElement(filterRuleWrapper(filter), start)
}

// UnmarshalXML - decodes XML data.
func (filter *FilterRule) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
	// Make subtype to avoid recursive UnmarshalXML().

)

// Reader - JSON record reader for S3Select.
type Reader struct {
	args       *ReaderArgs
	decoder    *jstream.Decoder
	valueCh    chan *jstream.MetaValue
	readCloser io.ReadCloser
}

// Read - reads single record.
func (r *Reader) Read(dst sql.Record) (sql.Record, error) {
	v, ok := <-r.valueCh
	if !ok {
		if err := r.decoder.Err(); err != nil {
			return nil, errJSONParsingError(err)
		}
		return nil, io.EOF
	}

          // otherwise try to presize a StringBuilder
          // it is kind of lame that we need to construct a decoder to access this value.
          // if this is a concern we could add special cases for some known charsets (like utf8)
          // or we could avoid inputstreamreader and use the decoder api directly
          // TODO(lukes): in a real implementation we would need to handle overflow conditions

          // otherwise try to presize a StringBuilder
          // it is kind of lame that we need to construct a decoder to access this value.
          // if this is a concern we could add special cases for some known charsets (like utf8)
          // or we could avoid inputstreamreader and use the decoder api directly
          // TODO(lukes): in a real implementation we would need to handle overflow conditions

// Used to detect if lifecycle.Rule contained a DelMarkerExpiration element.
func (de DelMarkerExpiration) Empty() bool {
	return de.Days == 0
}

// UnmarshalXML decodes a single XML element into a DelMarkerExpiration value
func (de *DelMarkerExpiration) UnmarshalXML(dec *xml.Decoder, start xml.StartElement) error {
	type delMarkerExpiration DelMarkerExpiration
	var dexp delMarkerExpiration
	err := dec.DecodeElement(&dexp, &start)
	if err != nil {

func (n NoncurrentVersionExpiration) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
	if n.IsNull() {
		return nil
	}
	type noncurrentVersionExpirationWrapper NoncurrentVersionExpiration
	return e.EncodeElement(noncurrentVersionExpirationWrapper(n), start)
}

// UnmarshalXML decodes NoncurrentVersionExpiration
func (n *NoncurrentVersionExpiration) UnmarshalXML(d *xml.Decoder, startElement xml.StartElement) error {

}

// MarshalXML - encodes to XML data.
func (arn ARN) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
	return e.EncodeElement(arn.String(), start)
}

// UnmarshalXML - decodes XML data.
func (arn *ARN) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
	var s string
	if err := d.DecodeElement(&s, &start); err != nil {
		return err
	}