🎯Core Definition
Query Rewriting & Sub-Query Decomposition is a core Pre-Retrieval RAG optimization technique that transforms raw user prompts into structured retrieval intents; using specialized prompts or fine-tuned LLMs, it performs coreference resolution (e.g., resolving 'its latest report' into 'Apple Inc. 2026 Q2 Financial Report'), synonym query expansion, and breaks complex multi-hop queries down into parallel or sequential atomic sub-queries that query the index independently before consolidating.
💡Use Cases
Multi-turn conversational RAG, multi-entity comparative analysis (e.g., 'Compare Nvidia and Qualcomm newest chip efficiency and price'), and ambiguous long-tail questions.
⚡Key Problems Solved
Raw user questions are colloquially ambiguous, pronoun-laden, and multi-faceted; searching composite queries directly yields poor vector similarity and misses cross-document facts; decomposing into atomic queries and aggregating results unlocks multi-hop reasoning.