PAIRS: Parametric-Verified Adaptive Information Retrieval and Selection for Efficient RAG

TL;DR

PAIRS is a training-free framework that adaptively combines parametric and external knowledge to improve the efficiency and accuracy of retrieval-augmented generation systems, reducing unnecessary retrievals and enhancing answer quality.

Contribution

PAIRS introduces a novel dual-path generation and adaptive retrieval mechanism that dynamically decides when and what to retrieve, significantly improving RAG system efficiency and accuracy without additional training.

Findings

Reduces retrieval costs by approximately 25%.

Achieves +1.1% EM and +1.0% F1 improvements on QA benchmarks.

Effectively filters irrelevant documents through adaptive selection.

Abstract

Retrieval-Augmented Generation (RAG) has become a cornerstone technique for enhancing large language models (LLMs) with external knowledge. However, current RAG systems face two critical limitations: (1) they inefficiently retrieve information for every query, including simple questions that could be resolved using the LLM's parametric knowledge alone, and (2) they risk retrieving irrelevant documents when queries contain sparse information signals. To address these gaps, we introduce Parametric-verified Adaptive Information Retrieval and Selection (PAIRS), a training-free framework that integrates parametric and retrieved knowledge to adaptively determine whether to retrieve and how to select external information. Specifically, PAIRS employs a dual-path generation mechanism: First, the LLM produces both a direct answer and a context-augmented answer using self-generated pseudo-context. When these outputs converge, PAIRS bypasses external retrieval entirely, dramatically improving the RAG system's efficiency. For divergent cases, PAIRS activates a dual-path retrieval (DPR) process guided by both the original query and self-generated contextual signals, followed by an Adaptive Information Selection (AIS) module that filters documents through weighted similarity to both sources. This simple yet effective approach can not only enhance efficiency by eliminating unnecessary retrievals but also improve accuracy through contextually guided retrieval and adaptive information selection. Experimental results on six question-answering (QA) benchmarks show that PAIRS reduces retrieval costs by around 25% (triggering for only 75% of queries) while still improving accuracy-achieving +1.1% EM and +1.0% F1 over prior baselines on average.