What a rewriter actually fixes
Query rewriting is the cheapest high-impact upgrade you can make to a RAG pipeline. One LLM call generates a small set of diverse reformulations of the user question, and you run retrieval once per reformulation. The fused result covers more of the relevant vector space than any single query could.
Matching exercise: Match failure modes to whether a rewriter helps
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A good rewriter prompt asks for diverse variants: one keyword-heavy phrasing, one natural-language question, and a paraphrase with different vocabulary. Diversity matters more than quantity. Three different phrasings outperform ten near-duplicates because they hit different regions of the embedding space.
Quiz: Quiz
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