“…trieve a set of relevant information to improve the model performance under the merit that an openbook exam is easier than a close-book exam. Recent success on various NLP tasks has shown the effectiveness of retrieval augmented models in improving the quality of neural NLP models, such as language modeling (Khandelwal et al, 2019;, question answering (Guu et al, 2020;Lewis et al, 2020a,b;Xiong et al, 2020), text classification (Lin et al, 2021b), dialog generation Thulke et al, 2021;Weston et al, 2018) and neural machine translation (Khandelwal et al, 2019;Meng et al, 2021a;Wang et al, 2021).…”