ColBERT và truy xuất đa vectơ

ColBERT independently encodes query and document tokens into contextual vectors, then uses late interaction to score their match with MaxSim. Precomputing document vectors avoids running a joint transformer for every query-document pair, while query encoding and token-level similarity still occur at search time. ColBERTv2 adds residual compression to reduce the stored index. A multi-vector index stores more information per document than a single-vector representation and can require more storage. These are method and system trade-offs, not claims about market adoption or product-database roadmaps. ColPali is a separate vision-language retrieval model that embeds images of document pages as multi-vector representations and uses late interaction; its paper evaluates visually rich document-retrieval benchmarks. These are paper results, not evidence of production prevalence or RAG answer-quality gains. In a two-stage retrieval pipeline, a first-stage retriever can find a candidate set and ColBERT can rerank those candidates using MaxSim. This is a design pattern for evaluation, not evidence of a particular production deployment.