RAG Flow Diagram (2026): How Retrieval‑Augmented Generation Works End‑to‑End

By Paath.online15 March 20267 min read

If you’ve built a RAG project once, you know it’s not “just embeddings + a prompt.” A real RAG system has ingestion, indexing, retrieval, re-ranking, prompt assembly, and evaluation. Here’s a clear flow diagram showing how it works.

RAG (Retrieval‑Augmented Generation) — End‑to‑End Flow (2026)1) Ingestion (build the knowledge base)2) Retrieval (find the right context)3) Generation (answer with citations)DocumentsPDFs • websites • notes • docs • DB exportsParse & CleanOCR (if scanned) • remove boilerplate • keep headingsnormalize whitespace • keep links/tables where neededChunksplit by headings • size/overlap • keep metadataadd source URL • section title • page numberEmbed (optional)turn chunks into vectors for semantic searchor skip embeddings for “vectorless” RAGIndex / StoreVector DB (pgvector, Pinecone, Weaviate)Keyword/BM25 (Elasticsearch) • hybrid indexAlso store chunk metadata + source for citationsUser Queryquestion or task instructionRetrieve Candidatesvector search (embeddings) and/or BM25 keyword searchfilters: doc type, date, tags, permissionsRe-rank & Selectcross-encoder / LLM re-rank • dedupe • pick top-kkeep citation pointers (source + section)Prompt Assemblysystem instructions + user question+ selected context chunks + citation rulesoptionally: tool outputs, tables, code snippetsLLM / Modelgenerates answer grounded in retrieved contextcan call tools (search, DB, calculator) if allowedFinal Answerclear response + citations (source/section/page)show uncertainty when context is missingEvaluate & Improvefeedback • test set • monitoring • refresh indexchunks + metadatatop‑k chunks + citationsrefresh / improve indexIngestionIndex/StoreRetrievalGeneration

How to Read This Diagram

  • Ingestion (left): your knowledge base is built once, then refreshed when docs change.
  • Retrieval (middle): for each query, you fetch candidate chunks and select the best few.
  • Generation (right): the LLM answers using the selected context, ideally with citations.

Vector RAG vs Vectorless RAG (Where It Fits)

Notice the “Embed (optional)” box. If you skip embeddings and rely on keyword/BM25 + structured navigation, you’re doing vectorless RAG. If you include embeddings and vector search, you’re doing vector RAG. Many production systems are hybrid.

Read: Vector RAG vs Vectorless RAG (2026) →

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