Query Expansion Is More Than Generation: Improving Dense Retrieval through Better Integration

2026-08-26

AI Summary

研究解决了查询扩展与密集检索器集成不佳的问题，提出AnchorQE方法，通过无监督在线策略估计插值因子，提高检索效果。

Abstract

Large language models (LLMs) can generate query expansions without task-specific training, yet the same expansions often make a frozen dense retriever worse. We identify an underexplored factor: prior work has often focused on what text is generated, while how generated text is incorporated into dense retrievers has received less systematic attention. By holding generated expansions fixed, we show that performance degradation can often be attributed to the integration method itself. We introduce AnchorQE, a training-free method that separately encodes the original query and its expansion before interpolating them. The interpolation factor is estimated using an unsupervised online strategy that operates over a small part of the unlabeled test stream. Intuitively, our strategy assigns high expansion trust only when expansions are both retrieval-strong and consistent with the original query's retrieved evidence. We show that AnchorQE improves retrieval effectiveness by up to 12.89% when compared to widely-used expansion-only or text-level concatenation baselines across TREC-DL, LoTTE, and BEIR. Further, we show that our online strategy to estimate the interpolation factor outperforms a fixed weight tuned on a development partition by up to 3.81%.

Problem

• query expansion
• dense retrieval
• integration method

Innovation

• AnchorQE
• query expansion
• dense retrieval
• interpolation factor
• unsupervised online strategy