REAR: Retrieve, Expand and Refine for Effective Multitable Retrieval
Answering natural language queries over re- lational data often requires retrieving and rea- soning over multiple tables, yet most retrievers optimize only for query–table relevance and ignore table–table compatibility. We introduce REAR (Retrieve, Expand and Refine), a three- stage, LLM-free framework that separates se- mantic relevance from structural joinability for efficient, high-fidelity multi-table retrieval. REAR (i) retrieves query-aligned tables, (ii) ex- pands these with structurally joinable tables via fast, precomputed column-embedding compar- isons, and (iii) refines them by pruning noisy or weakly related candidates. Empirically, REAR is retriever-agnostic and consistently improves dense/ sparse retrievers on complex table QA datasets (BIRD, MMQA, and Spider) by im- proving both multi-table retrieval quality and downstream SQL execution. Despite...