RAG Uses Three-Layer Hierarchical Indexing
thisguyknowsai · x · 2026-07-11
This covers Technique 2: Hierarchical Indexing.
The author argues a single index is insufficient, so the knowledge base is split into three layers:
- Summary index: for high-level overview questions
- Chunk index: for regular paragraph retrieval
- Sentence index: for precise fact location
A query router decides which layer to hit based on question type: macro questions go to summary, detailed facts go to sentence.
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