Course contents
On this page
Lesson plan 12: Specialized access paths
Explain the access patterns served by columnar, inverted, time-series, spatial, and vector indexes.
Placement: Part 2: Representing and locating data.
Prerequisites: Lesson 11: Log-structured storage, plus the earlier dependency chain.
Learning outcomes
- Explain the access patterns served by columnar, inverted, time-series, spatial, and vector indexes.
- Separate candidate generation from exact filtering or reranking.
- Evaluate specialized indexes using update cost, recall or precision, pruning effectiveness, and retained state.
- Separate a general mechanism, a documented implementation choice, and an illustrative numerical assumption.
Teaching sequence
- Establish the motivating situation: One system must support transactional lookups, analytics, text search, and nearest-neighbor retrieval.
- Introduce the vocabulary and the correctness obligation before an optimization. Define columnar access, inverted indexes, time series.
- Develop the mechanism: Explain each access path’s candidate reduction and residual checking; distinguish exact results from recall tradeoffs.
- Follow the complete worked example: Scanning 3 of 100 equal-width columns reduces uncompressed column bytes to 3%. Explain the assumptions, intermediate units, and limiting interpretation.
- Extend the scenario to changed load, skew, or failure, explaining spatial indexing, vector search, approximation.
- Connect the mechanism to a documented implementation and an alternative with a different workload fit. Close by stating the remaining cost and the next lesson dependency.
Required chapter material
Use a complete execution trace or worked calculation, supported by an annotated static diagram or table. Include language-neutral pseudocode or labeled SQL when it clarifies the mechanism. State preconditions, ownership, visibility, and failure boundaries for algorithms. Describe operational costs as well as the normal path. All questions raised in the narrative must be resolved in the text.
Visual explanation
A candidate-selection pipeline separates index lookup from residual verification; contrasting query shapes show why one access path cannot serve every predicate equally. The accompanying prose explains the arrows, state changes, or table entries so the lesson remains understandable in a plain Markdown reader.
Editorial checks
Confirm that the numerical example agrees with its units and assumptions. Check that a faster path preserves the stated contract, or explicitly identify the changed guarantee. Keep hypothetical figures separate from product measurements. Explain both an appropriate use and a limitation of the case design. Check terminology against the glossary and links against the course index.