Hello McCoy. "DocValues", "KnnVectors" and "Postings" are three core principally different APIs/data structures ie docValues is data column; and postings is inverted index. By default codec defines these three formats for all fields. And per-field wrappers allow configuring separate formats for a particular field, returning it by field name. I usually need to experiment with one or a few fields and keep remaining fields with the default format, so per-field wrappers are usually quite an intuitive thing.
On Tue, Oct 25, 2022 at 7:36 PM MyCoy Z <mycoy.zh...@gmail.com> wrote: > Hi, Everyone: > > I just start studying lucene's source code. > > I'm confused about those per-field formats, in this package of " > *org.apache.lucene.codecs.perfield*" > > There are many formats in lucene's codec. But there are only 3 per-field > formats: "DocValues", "KnnVectors" and "Postings". > > So, what is the purpose of those three per-field formats? > Why "DocValues", "KnnVectors" and "Postings" are so special that they need > those per-field formats? > > For example, I've studied the "KnnVectors" a little. > The "PerFieldKnnVectorsFormat.FieldsWriter" acutally uses the > "Lucene94HnswVectorsFormat". > But why do we have this kind of structures? > > Thanks & Regards > > MyCoy > -- Sincerely yours Mikhail Khludnev
