Class Lucene40StoredFieldsFormat

Lucene 4.0 Stored Fields Format.

Stored fields are represented by two files:

1. The field index, or .fdx file.

   This is used to find the location within the field data file of the fields of a particular document. Because it contains fixed-length data, this file may be easily randomly accessed. The position of document n 's field data is the Uint64 (WriteInt64(Int64)) at n*8 in this file.

   This contains, for each document, a pointer to its field data, as follows:

   • FieldIndex (.fdx) --> <Header>, <FieldValuesPosition> ^SegSize
   • Header --> CodecHeader (WriteHeader(DataOutput, String, Int32))
   • FieldValuesPosition --> Uint64 (WriteInt64(Int64))

2. The field data, or .fdt file.

   This contains the stored fields of each document, as follows:

   • FieldData (.fdt) --> <Header>, <DocFieldData> ^SegSize
   • Header --> CodecHeader (WriteHeader(DataOutput, String, Int32))
   • DocFieldData --> FieldCount, <FieldNum, Bits, Value> ^FieldCount
   • FieldCount --> VInt (WriteVInt32(Int32))
   • FieldNum --> VInt (WriteVInt32(Int32))
   • Bits --> Byte (WriteByte(Byte))
     • low order bit reserved.
     • second bit is one for fields containing binary data
     • third bit reserved.
     • 4th to 6th bit (mask: 0x7<<3) define the type of a numeric field:
       • all bits in mask are cleared if no numeric field at all
       • 1<<3: Value is Int
       • 2<<3: Value is Long
       • 3<<3: Value is Int as Float (as of Int32BitsToSingle(Int32)
       • 4<<3: Value is Long as Double (as of
   • Value --> String | BinaryValue | Int | Long (depending on Bits)
   • BinaryValue --> ValueSize, < Byte (WriteByte(Byte)) >^ValueSize
   • ValueSize --> VInt (WriteVInt32(Int32))