The retriever-reader pipeline has shown promising performance in open-domain QA but suffers from a very slow inference speed. Recently proposed question retrieval models tackle this problem by indexing question-answer pairs and searching for similar questions. These models have shown a significant increase in inference speed, but at the cost of lower QA performance compared to the retriever-reader models. This paper proposes a two-step question retrieval model, SQuID (Sequential Question-Indexed Dense retrieval) and distant supervision for training. SQuID uses two bi-encoders for question retrieval. The first-step retriever selects top-k similar questions, and the second-step retriever finds the most similar question from the top-k questions. We evaluate the performance and the computational efficiency of SQuID. The results show that SQuID significantly increases the performance of existing question retrieval models with a negligible loss on inference speed.
@article{arxiv.2205.09393,
title = {Two-Step Question Retrieval for Open-Domain QA},
author = {Yeon Seonwoo and Juhee Son and Jiho Jin and Sang-Woo Lee and Ji-Hoon Kim and Jung-Woo Ha and Alice Oh},
journal= {arXiv preprint arXiv:2205.09393},
year = {2022}
}