Hello, I've tried to catch up on the vector API and I have the following questions. I've tried to read through discussions on JIRA first in case it had been covered, but it's possible I missed some relevant ones.
Should VectorValues#search be on VectorReader instead? It felt a bit odd to me to have the search logic on the iterator. Do we need SearchStrategy.NONE? Documentation suggests that it allows storing vectors but that NN search won't be supported. This looks like a use-case for binary doc values to me? It also slightly caught me by surprise due to the inconsistency with IndexOptions.NONE, which means "do not index this field" (and likewise for DocValuesType.NONE), so I first assumed that SearchStrategy.NONE also meant "do not index this field as a vector". While postings and doc-value formats allow per-field configuration via PerFieldPostingsFormat/PerFieldDocValuesFormat, vectors use a different mechanism where VectorField#createHnswType sets attributes on the field type that the vectors writer then reads. Should we have a PerFieldVectorsFormat instead and configure these options via the vectors format? Should SearchStrategy constants avoid explicit references to HNSW? The rest of the API seems to try to be agnostic of the way that NN search is implemented. Could we make SearchStrategy only about the similarity metric that is used for vectors? This particular point seems discussed on LUCENE-9322 <https://issues.apache.org/jira/browse/LUCENE-9322> but I couldn't find the conclusion. Should we rename VectorFormat to VectorsFormat? This would be more consistent with other file formats that use the plural, like PostingsFormat, DocValuesFormat, TermVectorsFormat, etc.? -- Adrien
