---
phase: 12
phase_name: EXPLAIN + Typed Output
verified_at: "2026-03-02T14:30:00Z"
status: passed
score: 11/11
requirements: [EXPL-01, OUT-01]
---

# Phase 12 Verification Report: EXPLAIN + Typed Output

## Goal Achievement

**Phase Goal**: `EXPLAIN FROM semantic_query(...)` shows the expanded SQL, and `semantic_query` returns typed columns instead of all-VARCHAR

**Score**: 11/11 must-haves verified — **PASSED**

## Success Criteria

| # | Success Criterion | Status | Evidence |
|---|-------------------|--------|----------|
| 1 | `explain_semantic_view` outputs the expanded SQL that the extension generates | ✓ VERIFIED | `explain_semantic_view` registered in lib.rs:199, emits SQL lines in explain.rs:178; integration test asserts `-- Semantic View:`, `GROUP BY`, `test_orders` all present |
| 2 | A BIGINT aggregate metric returns a BIGINT column (not VARCHAR) | ✓ VERIFIED | bind() reads `column_types_inferred`, declares BIGINT output (table_function.rs:408), writes i64 (line 767); `query TI` + `query I` integration tests passing |
| 3 | A DATE time dimension returns typed DATE data (not VARCHAR) | ✓ VERIFIED | DATE→i32 via `date_str_to_epoch_days` (line 722), written as i32 (line 794); `query TI` for `typed_date_test` asserts "2024-01-01" + 5 and "2024-02-01" + 3 |

## Must-Haves Verification

### Plan 12-01: Model Fields

| Truth | Status |
|-------|--------|
| SemanticViewDefinition carries `output_type` on Dimension/Metric | ✓ VERIFIED |
| SemanticViewDefinition carries parallel `column_type_names` + `column_types_inferred` | ✓ VERIFIED |
| Old catalog JSON without these fields deserializes without error | ✓ VERIFIED |
| Unit tests for new fields pass under `cargo test` | ✓ VERIFIED (100 tests pass) |

### Plan 12-02: DDL + Inference + CAST

| Truth | Status |
|-------|--------|
| `create_semantic_view` registered and callable | ✓ VERIFIED (lib.rs:109) |
| `create_or_replace_semantic_view` registered | ✓ VERIFIED (lib.rs:122) |
| `create_semantic_view_if_not_exists` registered, silently no-ops | ✓ VERIFIED (lib.rs:135, integration test) |
| `define_semantic_view` / `define_or_replace_semantic_view` removed | ✓ VERIFIED (grep confirms absent from lib.rs) |
| DDL-time LIMIT 0 inference populates column_type_names + column_types_inferred | ✓ VERIFIED (define.rs:154-155) |
| In-memory databases skip inference | ✓ VERIFIED (conditional on persist_conn) |
| `explain_semantic_view` remains registered | ✓ VERIFIED (lib.rs:199) |
| `output_type` emits CAST in expanded SQL | ✓ VERIFIED (expand.rs + unit tests) |

### Plan 12-03: Typed Bind + Func

| Truth | Status |
|-------|--------|
| bind() reads column_types_inferred, declares typed output | ✓ VERIFIED (table_function.rs:340,408) |
| BIGINT metric declared as BIGINT, written as i64 | ✓ VERIFIED |
| DATE dimension declared as DATE, written as i32 (days-since-epoch) | ✓ VERIFIED |
| DOUBLE metric declared as DOUBLE, written as f64 | ✓ VERIFIED |
| Empty/invalid types fall back to VARCHAR | ✓ VERIFIED (INVALID|DECIMAL → VARCHAR) |
| NULL handling correct for typed columns | ✓ VERIFIED (set_null + null_positions pattern) |
| HUGEINT→BIGINT fix: 16-byte slot issue resolved | ✓ VERIFIED (Bug fix commit 7d8dda7) |

### Plan 12-04: Integration Tests

| Truth | Status |
|-------|--------|
| `make test_debug` passes with zero failures | ✓ VERIFIED (3x SUCCESS) |
| All `define_semantic_view` replaced in test files | ✓ VERIFIED (grep = 0) |
| `create_semantic_view_if_not_exists` tested | ✓ VERIFIED (4 occurrences, phase2_ddl.test:262-284) |
| `explain_semantic_view` test returns expanded SQL | ✓ VERIFIED (7 occurrences in phase4_query.test) |
| BIGINT metric uses `query I` | ✓ VERIFIED (query TI rowsort + query I assertions) |
| DATE time dimension asserts typed format | ✓ VERIFIED (query TI with "2024-01-01" values) |

## Artifact Verification

| Artifact | Exists | Substantive | Wired | Status |
|----------|--------|-------------|-------|--------|
| `src/model.rs` | ✓ | ✓ output_type + column_types_inferred fields | ✓ used by define.rs + table_function.rs | ✓ VERIFIED |
| `src/lib.rs` | ✓ | ✓ 4 DDL registrations + explain | ✓ wired to define.rs handlers | ✓ VERIFIED |
| `src/ddl/define.rs` | ✓ | ✓ DDL-time inference + if_not_exists | ✓ invoked via lib.rs scalar registration | ✓ VERIFIED |
| `src/expand.rs` | ✓ | ✓ CAST codegen for output_type | ✓ called from table_function.rs bind() | ✓ VERIFIED |
| `src/query/table_function.rs` | ✓ | ✓ typed bind()+func() + HUGEINT fix | ✓ registered in lib.rs | ✓ VERIFIED |
| `src/query/explain.rs` | ✓ | ✓ emits expanded SQL lines | ✓ registered as explain_semantic_view | ✓ VERIFIED |
| `test/sql/phase2_ddl.test` | ✓ | ✓ DDL rename + if_not_exists test | ✓ in TEST_LIST, loaded by runner | ✓ VERIFIED |
| `test/sql/phase4_query.test` | ✓ | ✓ EXPL-01 + OUT-01 typed assertions | ✓ in TEST_LIST, loaded by runner | ✓ VERIFIED |
| `.planning/REQUIREMENTS.md` | ✓ | ✓ EXPL-01 + OUT-01 marked [x] | ✓ N/A | ✓ VERIFIED |

## Requirements Coverage

| Requirement | Description | Status |
|-------------|-------------|--------|
| EXPL-01 | explain_semantic_view returns expanded SQL | ✓ SATISFIED |
| OUT-01 | semantic_view returns typed columns (BIGINT, DATE, etc.) | ✓ SATISFIED |

## Anti-Pattern Scan

Files scanned: src/model.rs, src/lib.rs, src/ddl/define.rs, src/expand.rs, src/query/table_function.rs, test/sql/phase2_ddl.test, test/sql/phase4_query.test

| Pattern | Matches | Severity |
|---------|---------|----------|
| TODO/FIXME/XXX/HACK | 0 | ✓ Clean |
| Placeholder content | 0 | ✓ Clean |
| Empty returns | 0 blockers | ✓ Clean |

## Human Verification

**None required.** All three success criteria are verifiable programmatically:
- `make test_debug` confirms explain_semantic_view returns correct SQL content
- `query I` / `query TI` type specifiers confirm BIGINT typed output (SQLLogicTest would fail if VARCHAR returned)
- `query TI` for typed_date_test confirms DATE values formatted correctly

## Summary

Phase 12 is complete. The semantic_views extension now:
1. Exposes `explain_semantic_view` for query transparency (EXPL-01)
2. Returns typed columns (BIGINT for count/sum metrics, DATE for time dimensions) instead of all-VARCHAR (OUT-01)
3. Uses DDL-time LIMIT 0 inference to persist column types in the catalog JSON
4. Renames DDL functions to `create_semantic_view*` family

Notable fix: HUGEINT→BIGINT output declaration prevents 16-byte slot corruption when `sum(INTEGER)` produces HUGEINT. Fix committed in 7d8dda7.

**Verdict: PASSED — Phase 12 goal achieved.**
