code: func (b *FieldInfosBuilder) AddOrUpdate(name string, fieldType IndexableFieldType) *FieldInfo {
  	// TODO: really, indexer shouldn't even call this method (it's only
  	// called from DocFieldProcessor); rather, each component in the
  	// chain should update what it "owns". E.g., fieldType.indexOptions()
  	// should be updated by maybe FreqProxTermsWriterPerField:
  	return b.addOrUpdateInternal(name, -1, fieldType.Indexed(), false,
  		fieldType.OmitNorms(), false,
  		fieldType.IndexOptions(), fieldType.DocValueType(), DocValuesType(0))
  }
docs: /*
  NOTE: this method does not carry over termVector booleans nor
  docValuesType; the indexer chain  (TermVectorsConsumerPerField,
  DocFieldProcessor) must set these fields when they succeed in
  consuming the document
  */