Popularized by the Differentiable Search Index, the emerging paradigm of
generative retrieval re-frames the classic information retrieval problem into a
sequence-to-sequence modeling task, forgoing external indices and encoding an
entire document corpus within a single Transformer. Although many different
approaches have been proposed to improve the effectiveness of generative
retrieval, they have only been evaluated on document corpora on the order of
100k in size. We conduct the first empirical study of generative retrieval
techniques across various corpus scales, ultimately scaling up to the entire MS
MARCO passage ranking task with a corpus of 8.8M passages and evaluating model
sizes up to 11B parameters. We uncover several findings about scaling
generative retrieval to millions of passages; notably, the central importance
of using synthetic queries as document representations during indexing, the
ineffectiveness of existing proposed architecture modifications when accounting
for compute cost, and the limits of naively scaling model parameters with
respect to retrieval performance. While we find that generative retrieval is
competitive with state-of-the-art dual encoders on small corpora, scaling to
millions of passages remains an important and unsolved challenge. We believe
these findings will be valuable for the community to clarify the current state
of generative retrieval, highlight the unique challenges, and inspire new
research directions.

本文对生成式检索技术进行了第一次经验研究，通过使用合成查询作为文档表示进行索引，以及调整内部架构，探索了在不同语料库规模下扩展生成式检索的几个关键点，发现在小规模语料库上生成式检索和最先进的双编码器具有竞争力，但在数百万篇章的大规模语料库上实现可扩展性仍然是一个重要的未解决问题。