When to Use an LLM Knowledge Graph or a Vector RAG
Blog post from n8n
Retrieval-augmented generation (RAG) grounds large language model responses in external information to reduce hallucinations, with vector RAG retrieving semantically similar text passages and knowledge graph RAG representing facts as entity-relationship triples that support multi-hop reasoning across sources. Vector RAG is generally simpler and less costly for questions answered by a small set of related documents, while knowledge graphs are better suited to complex, relationship-heavy queries requiring traceability, though they demand greater construction, validation, entity resolution, and maintenance efforts. Knowledge graphs can be built from unstructured text through LLM-based extraction of entities and relationships, using either predefined schemas for consistency or flexible schema-free approaches for discovery, with domain ontologies and validation helping improve quality. A hybrid approach can combine semantic vector retrieval with graph traversal, and the n8n automation platform is presented as a tool for building, monitoring, debugging, and evolving vector, graph, or hybrid RAG workflows through vector-store integrations, entity extraction, AI-agent orchestration, and graph database connections.
| Trend | Post Mentions | Total Month Mentions | Posts | Companies | MoM |
|---|---|---|---|---|---|
| RAG | 23 | 873 | 223 | 83 | +1% |
| LLM | 19 | 6,513 | 1,228 | 231 | +8% |
| AI Agents | 4 | 6,921 | 1,636 | 267 | +23% |
| Vector Search | 4 | 1,956 | 410 | 132 | +17% |
| Multi-agent systems | 3 | 325 | 118 | 62 | -30% |
| Data Pipeline | 1 | 401 | 160 | 72 | +47% |
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