---
phase: 11.1-review-possible-ddl-and-query-syntax-options-and-bring-it-as-close-as-we-can-to-snowflake-semantic-views
plan: "03"
subsystem: database
tags: [rust, expand, sql-codegen, join, semantic-views]

requires:
  - phase: 11.1-01
    provides: "JoinColumn, TableRef, Join.join_columns, SemanticViewDefinition.tables"

provides:
  - "JOIN ON clause generation from join_columns column pairs"
  - "Alias-to-physical-table resolution in resolve_joins"
  - "Table-qualified dimension/metric name lookup (alias.name syntax)"

affects:
  - "11.1-04 (define.rs uses expand.rs indirectly via query path)"
  - "11.1-05 (test files exercise the new expand behavior)"

tech-stack:
  added: []
  patterns:
    - "Extract JOIN ON clause logic to append_join_on_clause() helper to satisfy clippy::too_many_lines"
    - "Use map_or() instead of map().unwrap_or() for clippy::map_unwrap_or"
    - "Use is_some_and() instead of map().unwrap_or(false) for clippy::map_unwrap_or"

key-files:
  created: []
  modified:
    - "src/expand.rs"

key-decisions:
  - "append_join_on_clause() helper extracted to satisfy clippy::too_many_lines on expand()"
  - "resolve_joins() receives def parameter to resolve alias source_table values to physical names"
  - "Qualified name fallback: o.region falls back to bare 'region' if no source_table='o' match"

patterns-established:
  - "Alias resolution pattern: def.tables.iter().find(alias match).map_or(physical, alias)"

requirements-completed:
  - DDL-04

duration: 15min
completed: 2026-03-02
---

# Phase 11.1 Plan 03: expand.rs JOIN Codegen + Table-Qualified Names Summary

**JOIN ON clause generated from join_columns column pairs with alias resolution; find_dimension/find_metric support alias.name qualified lookup**

## Performance

- **Duration:** 15 min
- **Started:** 2026-03-02T00:20:00Z
- **Completed:** 2026-03-02T00:35:00Z
- **Tasks:** 1
- **Files modified:** 1

## Accomplishments
- Added `append_join_on_clause()` helper that generates alias-qualified ON clauses from `join_columns` pairs; falls back to legacy `join.on` string when `join_columns` is empty
- Updated `resolve_joins()` to accept `def` and resolve alias `source_table` values (e.g., `"c"`) to physical table names (e.g., `"customers"`) before matching against `join.table`
- Updated `find_dimension()` and `find_metric()` to support `alias.name` qualified lookup with `source_table` matching; falls back to bare-name for backward compat
- Added 7 new unit tests in `phase11_1_expand_tests` covering all specified behaviors
- All 92 tests pass (85 unit + 6 proptest + 1 doctest)

## Task Commits

1. **Task 1: Update JOIN codegen + table-qualified name resolution** - `bbb22e8` (feat)

## Files Created/Modified
- `src/expand.rs` - append_join_on_clause, updated resolve_joins, find_dimension, find_metric

## Decisions Made
- `append_join_on_clause()` extracted to avoid clippy::too_many_lines on `expand()`
- `resolve_joins()` receives `def` parameter instead of separate `tables` slice — cleaner API
- Qualified dimension/metric fallback uses bare name only — not alias.bare (which could be ambiguous)

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 1 - Bug] resolve_joins needed alias-to-physical-table resolution**
- **Found during:** Task 1 (test join_columns_generates_on_clause failed)
- **Issue:** Dimensions with `source_table = "c"` (alias) didn't match `join.table = "customers"` (physical), so join was excluded
- **Fix:** Updated `resolve_joins` signature to accept `def` and added alias resolution via `def.tables`
- **Files modified:** src/expand.rs
- **Verification:** All phase11_1_expand_tests pass
- **Committed in:** bbb22e8

---

**Total deviations:** 1 auto-fixed (1 bug)
**Impact on plan:** Essential fix for the alias-based source_table pattern; no scope creep.

## Issues Encountered
None

## Next Phase Readiness
- expand.rs fully supports new join_columns model and alias.name dimension lookup
- Ready for Plan 04 (wire parse_args into DefineSemanticView; lib.rs rename)
- Plan 02 (parse_args.rs) can proceed independently in Wave 2

---
*Phase: 11.1-review-possible-ddl-and-query-syntax-options-and-bring-it-as-close-as-we-can-to-snowflake-semantic-views*
*Completed: 2026-03-02*
