Lucene99FlatVectorsFormat

Lucene 9.9 flat vector format, which encodes numeric vector values

.vec (vector data) file

For each field:

• Vector data ordered by field, document ordinal, and vector dimension. When the vectorEncoding is BYTE, each sample is stored as a single byte. When it is FLOAT32, each sample is stored as an IEEE float in little-endian byte order.

• DocIds encoded by IndexedDISI.writeBitSet, note that only in sparse case

• OrdToDoc was encoded by org.gnit.lucenekmp.util.packed.DirectMonotonicWriter, note that only in sparse case

.vemf (vector metadata) file

For each field:

• int32 field number

• int32 vector similarity function ordinal

• vlong offset to this field's vectors in the .vec file

• vlong length of this field's vectors, in bytes

• vint dimension of this field's vectors

• int the number of documents having values for this field

• int8 if equals to -2, empty - no vector values. If equals to -1, dense – all documents have values for a field. If equals to 0, sparse – some documents missing values.

• DocIds were encoded by IndexedDISI.writeBitSet

• OrdToDoc was encoded by org.gnit.lucenekmp.util.packed.DirectMonotonicWriter, note that only in sparse case