Tabular data is frequently captured in image form across a wide range of real-world scenarios such as financial reports, handwritten records, and document scans. These visual representations pose unique challenges for machine understanding, as they combine both structural and visual complexities. While recent advances in Multimodal Large Language Models (MLLMs) show promising results in table understanding, they typically assume the relevant table is readily available. However, a more practical scenario involves identifying and reasoning over relevant tables from large-scale collections to answer user queries. To address this gap, we propose , a framework that enables MLLMs to answer queries over large collections of table images. Our approach first retrieves candidate tables using jointly trained visual-text foundation models, then leverages MLLMs to perform fine-grained reranking of these candidates, and finally employs MLLMs to reason over the selected tables for answer generation. Through extensive experiments on a newly constructed dataset comprising 88,161 training and 9,819 testing samples across 8 benchmarks with 48,504 unique tables, we demonstrate that our framework significantly outperforms existing methods by 7.0% in retrieval recall and 6.1% in answer accuracy, offering a practical solution for real-world table understanding tasks.

Large language models (LLMs) have demonstrated impressive capabilities in generating human-like text and have been shown to store factual knowledge within their extensive parameters. However, models like ChatGPT can still actively or passively generate false or misleading information, increasing the challenge of distinguishing between human-created and machine-generated content. This poses significant risks to the authenticity and reliability of digital communication. This work aims to enhance retrieval models’ ability to identify the authenticity of texts generated by large language models, with the goal of improving the truthfulness of retrieved texts and reducing the harm of false information in the era of large models. Our contributions include: (1) we construct a diverse dataset of authentic human-authored texts and highly deceptive AI-generated texts from various domains; (2) we propose a self-supervised training method, RetrieverGuard, that enables the model to capture textual rules and styles of false information from the corpus without human-labelled data, achieving higher accuracy and robustness in identifying misleading and highly deceptive AI-generated content.