Package org.apache.lucene.codecs.lucene46

Class Lucene46FieldInfosFormat

  • public final class Lucene46FieldInfosFormat
extends FieldInfosFormat
    Lucene 4.6 Field Infos format.

    Field names are stored in the field info file, with suffix .fnm.

    FieldInfos (.fnm) --> Header,FieldsCount, <FieldName,FieldNumber, FieldBits,DocValuesBits,DocValuesGen,Attributes> FieldsCount

    Data types:

    Field Descriptions:
    • FieldsCount: the number of fields in this file.
    • FieldName: name of the field as a UTF-8 String.
    • FieldNumber: the field's number. Note that unlike previous versions of Lucene, the fields are not numbered implicitly by their order in the file, instead explicitly.
    • FieldBits: a byte containing field options.
      • The low-order bit is one for indexed fields, and zero for non-indexed fields.
      • The second lowest-order bit is one for fields that have term vectors stored, and zero for fields without term vectors.
      • If the third lowest order-bit is set (0x4), offsets are stored into the postings list in addition to positions.
      • Fourth bit is unused.
      • If the fifth lowest-order bit is set (0x10), norms are omitted for the indexed field.
      • If the sixth lowest-order bit is set (0x20), payloads are stored for the indexed field.
      • If the seventh lowest-order bit is set (0x40), term frequencies and positions omitted for the indexed field.
      • If the eighth lowest-order bit is set (0x80), positions are omitted for the indexed field.
    • DocValuesBits: a byte containing per-document value types. The type recorded as two four-bit integers, with the high-order bits representing norms options, and the low-order bits representing DocValues options. Each four-bit integer can be decoded as such:
      • 0: no DocValues for this field.
      • 1: NumericDocValues. (FieldInfo.DocValuesType.NUMERIC)
      • 2: BinaryDocValues. (DocValuesType#BINARY)
      • 3: SortedDocValues. (DocValuesType#SORTED)
    • DocValuesGen is the generation count of the field's DocValues. If this is -1, there are no DocValues updates to that field. Anything above zero means there are updates stored by DocValuesFormat.
    • Attributes: a key-value map of codec-private attributes.