Generative retrieval is a promising new paradigm in text retrieval that
generates identifier strings of relevant passages as the retrieval target. This
paradigm leverages powerful generation models and represents a new paradigm
distinct from traditional learning-to-rank methods. However, despite its rapid
development, current generative retrieval methods are still limited. They
typically rely on a heuristic function to transform predicted identifiers into
a passage rank list, which creates a gap between the learning objective of
generative retrieval and the desired passage ranking target. Moreover, the
inherent exposure bias problem of text generation also persists in generative
retrieval. To address these issues, we propose a novel framework, called LTRGR,
that combines generative retrieval with the classical learning-to-rank
paradigm. Our approach involves training an autoregressive model using a
passage rank loss, which directly optimizes the autoregressive model toward the
optimal passage ranking. This framework only requires an additional training
step to enhance current generative retrieval systems and does not add any
burden to the inference stage. We conducted experiments on three public
datasets, and our results demonstrate that LTRGR achieves state-of-the-art
performance among generative retrieval methods, indicating its effectiveness
and robustness