Topic 2: Chunk-Relationship Patterns
8 min read·21 Sept 2026
The shared idea: search one thing, answer with another. A small unit is easy to find; a larger unit is easy to understand. These patterns change what you index and what you return.
| Pattern | Index | Return | Index cost | Best for |
|---|---|---|---|---|
| Parent-document | Sentences or small chunks | The parent section or document | Medium | Procedures, rules with exceptions |
| Sentence-window | Sentences | The sentence plus neighbours | Medium | Dense factual prose |
| Hierarchical | Summaries and details | Details from the chosen documents | High (summaries) | Broad questions over many documents |
| RAPTOR | Leaves and cluster summaries | Whichever level matched | High (clustering + summaries) | "Overall" and thematic questions |
| Contextual retrieval | Chunks with a generated situating sentence | The chunk or its document | High (one LLM call per chunk) | Look-alike chunks, pronouns |