---
phase: 03-expansion-engine
verified: 2026-02-25T00:00:00Z
status: passed
score: 5/5 must-haves verified
re_verification: false
---

# Phase 3: Expansion Engine Verification Report

**Phase Goal:** The expansion engine correctly generates SQL for all metric types, single-hop joins, GROUP BY inference, row filter composition, and identifier quoting — verified by unit and property tests against known-answer datasets
**Verified:** 2026-02-25
**Status:** passed
**Re-verification:** No — initial verification

---

## Goal Achievement

### Observable Truths (from Success Criteria)

| # | Truth | Status | Evidence |
|---|-------|--------|----------|
| 1 | The expand() function, called with a semantic view definition and a dimension+metric selection, produces a SQL string where every requested dimension appears in the GROUP BY clause | VERIFIED | `test_basic_single_dimension_single_metric`, `test_multiple_dimensions_multiple_metrics`, proptest `all_dimensions_in_group_by` (256 cases) all pass |
| 2 | The expand() function correctly infers JOIN clauses from entity relationships; requesting a metric from a joined table generates the correct JOIN without the user specifying it | VERIFIED | `test_join_included_when_dimension_needs_it`, `test_join_included_when_metric_needs_it`, `test_transitive_join_resolution`, `test_joins_emitted_in_declaration_order`, proptest `joins_only_when_needed` all pass |
| 3 | Requesting a dimension or metric name that does not exist produces a clear error message identifying the semantic view name and the unknown member name | VERIFIED | `test_unknown_dimension_error`, `test_unknown_metric_error`, `test_error_display_messages` pass; ExpandError variants contain view_name, name, available, and suggestion fields; Display impl verified |
| 4 | All SQL identifiers in emitted SQL are quoted with double-quotes, preventing reserved-word conflicts | VERIFIED | `test_identifier_quoting` (base_table="select" -> `"select"`), `test_basic_single_dimension_single_metric` (exact output match), `quote_ident` unit tests (4 cases), proptest `sql_structure_valid` (CTE name `"_base"`, FROM `"_base"`) |
| 5 | Property-based tests (proptest) verify that for any combination of valid dimensions and metrics, all requested dimensions appear in GROUP BY and the emitted SQL is syntactically valid | VERIFIED | 6 proptest properties x 256 cases each: `all_dimensions_in_group_by`, `all_dimensions_and_metrics_in_select`, `sql_structure_valid`, `joins_only_when_needed`, `filters_always_present`, `global_aggregate_no_group_by` — all pass |

**Score:** 5/5 truths verified

---

## Required Artifacts

### Plan 03-01 Artifacts

| Artifact | Expected | Status | Details |
|----------|----------|--------|---------|
| `src/expand.rs` | expand(), QueryRequest, ExpandError, quote_ident() | VERIFIED | 341 lines; all types present and substantive; 27 unit tests including 23 expand tests + 4 quote_ident tests |
| `src/model.rs` | Updated Dimension and Metric with optional source_table field | VERIFIED | Both structs have `#[serde(default)] pub source_table: Option<String>`; backward compat tests pass |
| `src/lib.rs` | pub mod expand declaration | VERIFIED | Line 2: `pub mod expand;` present |

### Plan 03-02 Artifacts

| Artifact | Expected | Status | Details |
|----------|----------|--------|---------|
| `src/expand.rs` | Join dependency resolution, name validation with fuzzy matching | VERIFIED | `suggest_closest()` (lines 11-27), `resolve_joins()` (lines 144-198), name validation in `expand()` (lines 246-288), join resolution call at line 291 |
| `Cargo.toml` | strsim dependency | VERIFIED | Line 35: `strsim = "0.11"` in `[dependencies]` |

### Plan 03-03 Artifacts

| Artifact | Expected | Status | Details |
|----------|----------|--------|---------|
| `tests/expand_proptest.rs` | Property-based tests using proptest! macro | VERIFIED | 292 lines; 6 proptest properties; `simple_definition()` and `joined_definition()` fixtures; `arb_query_request()` strategy |
| `Cargo.toml` | proptest dev-dependency | VERIFIED | Line 38: `proptest = "1.9"` in `[dev-dependencies]` |

---

## Key Link Verification

| From | To | Via | Status | Details |
|------|----|-----|--------|---------|
| `src/expand.rs` | `src/model.rs` | uses SemanticViewDefinition, Dimension, Metric | VERIFIED | Line 4: `use crate::model::{Join, SemanticViewDefinition};` — also uses Dimension, Metric via model imports in tests |
| `src/expand.rs` | `strsim` | levenshtein distance for fuzzy matching | VERIFIED | Line 15: `strsim::levenshtein(&query, &candidate.to_ascii_lowercase())` in `suggest_closest()` |
| `src/expand.rs` | `src/model.rs` | reads Join.table, Dimension.source_table, Metric.source_table | VERIFIED | `resolve_joins()` accesses `dim.source_table`, `met.source_table`, `join.table`, `join.on` |
| `tests/expand_proptest.rs` | `src/expand.rs` | uses expand(), QueryRequest, SemanticViewDefinition | VERIFIED | Lines 2-3: `use semantic_views::expand::{expand, QueryRequest}; use semantic_views::model::{...}` |
| `tests/expand_proptest.rs` | `proptest` | proptest! macro and subsequence strategy | VERIFIED | Line 1: `use proptest::prelude::*;`; proptest! macro used at line 136; `proptest::sample::subsequence` at lines 122-124 |

---

## Requirements Coverage

Requirements declared across all three plans: MODEL-01, MODEL-02, MODEL-03, MODEL-04, EXPAND-01, EXPAND-02, EXPAND-03, EXPAND-04, TEST-01, TEST-02

| Requirement | Source Plan | Description | Status | Evidence |
|-------------|------------|-------------|--------|----------|
| MODEL-01 | 03-01 | User can define named dimensions as arbitrary SQL column expressions | SATISFIED | Dimension struct with `name` + `expr` fields; `test_dimension_expression_not_quoted` verifies `date_trunc('month', created_at)` emitted verbatim |
| MODEL-02 | 03-01 | User can define named metrics as aggregation expressions | SATISFIED | Metric struct with `name` + `expr` fields; `test_basic_single_dimension_single_metric` verifies `sum(amount) AS "total_revenue"` |
| MODEL-03 | 03-02 | User can specify a base table and define explicit JOIN relationships | SATISFIED | SemanticViewDefinition has `base_table` + `joins: Vec<Join>`; `test_join_included_when_dimension_needs_it` verifies join emission |
| MODEL-04 | 03-01 | User can define row-level filter conditions always applied when view is queried | SATISFIED | `test_filters_and_composed`, `test_single_filter` verify WHERE clause; proptest `filters_always_present` verifies for all request subsets |
| EXPAND-01 | 03-01 | Extension automatically generates GROUP BY clause containing all requested dimensions | SATISFIED | `test_multiple_dimensions_multiple_metrics` verifies exact GROUP BY; proptest `all_dimensions_in_group_by` verifies over 256 cases |
| EXPAND-02 | 03-02 | Extension infers JOIN clauses from entity relationships | SATISFIED | `test_join_excluded_when_not_needed` confirms unneeded joins absent; `test_transitive_join_resolution` confirms multi-hop inference; proptest `joins_only_when_needed` verifies |
| EXPAND-03 | 03-02 | Extension validates dimension and metric names; invalid names produce clear error | SATISFIED | `test_unknown_dimension_error` asserts view_name, name, available, suggestion; `test_error_display_messages` verifies human-readable Display output |
| EXPAND-04 | 03-01 | All generated SQL identifiers are quoted to prevent reserved-word conflicts | SATISFIED | `quote_ident()` wraps all identifiers; `test_identifier_quoting` verifies reserved word "select" quoted; proptest `sql_structure_valid` verifies `"_base"` and `FROM "_base"` |
| TEST-01 | 03-01, 03-02 | Unit tests cover expansion engine without requiring DuckDB runtime | SATISFIED | 27 unit tests in `src/expand.rs`; run via `cargo test --lib -- expand::` in 0.00s with no DuckDB runtime needed |
| TEST-02 | 03-03 | Property-based tests (proptest) cover expansion engine invariants | SATISFIED | 6 proptest properties in `tests/expand_proptest.rs`; all pass with 256 cases each |

**No orphaned requirements.** All 10 declared requirement IDs from plan frontmatter are covered. REQUIREMENTS.md traceability table marks all 10 as Complete for Phase 3.

---

## Anti-Patterns Found

Scanned all modified files for stubs, placeholders, and red-flag patterns.

| File | Pattern | Finding | Severity |
|------|---------|---------|---------|
| `src/expand.rs` | `todo!()` stub | Not present — expand() is fully implemented (341 lines) | OK |
| `src/expand.rs` | `return null / return {}` | Not present | OK |
| `src/expand.rs` | Empty handlers | Not present | OK |
| `tests/expand_proptest.rs` | `proptest!` macro present | Confirmed — 6 tests with 256 cases each | OK |
| `Cargo.toml` | strsim, proptest present | Confirmed at correct versions | OK |

No anti-patterns found. No stubs, no placeholders, no TODO/FIXME comments in phase 3 files.

---

## Test Execution Results

Tests run during verification:

```
cargo test --lib -- expand::     -> 27 passed, 0 failed
cargo test --test expand_proptest -> 6 passed, 0 failed
cargo test --lib -- model::      -> 7 passed, 0 failed
cargo clippy -- -D warnings      -> clean (no warnings)
cargo test (full suite)          -> 42 passed, 3 failed (*)
```

(*) The 3 failing tests are `catalog::tests::{init_catalog_loads_from_sidecar, pragma_database_list_returns_file_path, sidecar_round_trip}` — these fail due to sandbox filesystem restrictions (`/tmp` write denied in the verification environment). They are pre-existing Phase 2 sidecar tests unrelated to Phase 3 work. All 27 expand unit tests, 7 model tests, 6 proptest tests, and 1 doctest pass.

---

## Human Verification Required

None. All success criteria are verifiable programmatically:

- GROUP BY correctness: verified by exact-match unit tests and proptest structural assertions
- JOIN inference: verified by positive (join present) and negative (join absent) unit tests and proptest
- Error messages: verified by Display output string assertions
- Identifier quoting: verified by exact-match SQL output tests
- Proptest consistency: confirmed by running 6 properties x 256 cases each — all green

---

## Summary

Phase 3 goal is fully achieved. The expansion engine delivers:

- A substantive, non-stub `expand()` function (341 lines) with complete GROUP BY inference, join dependency resolution (including transitive hops via fixed-point loop), filter AND-composition, and identifier quoting via `quote_ident()`
- 27 unit tests covering all known-answer cases for correctness (quote_ident, basic expansion, multi-dim/metric, global aggregates, filters, identifier quoting, expression passthrough, join inclusion/exclusion, transitive joins, name errors, duplicate errors, case insensitivity)
- 6 property-based tests (proptest, 256 cases each) verifying structural invariants hold for arbitrary valid dimension+metric subsets
- All 10 requirement IDs (MODEL-01..04, EXPAND-01..04, TEST-01..02) satisfied with direct evidence

---

_Verified: 2026-02-25_
_Verifier: Claude (gsd-verifier)_
