CharlesKWON
c6799a599e
Surfaced by complex-query benchmarking. Query like:
SELECT d.name AS dept, COUNT(*) AS n, SUM(o.amount) AS total
FROM dept d INNER JOIN emp e ON ... INNER JOIN ord o ON ...
GROUP BY d.name
returned exactly 1 row instead of 100. Removing the AS aliases made
it work correctly. Semantic bug, not a performance issue.
Root cause: TSqlAgg:GroupBy resolved each GROUP BY column by calling
FindColIdx against aFN — the output alias list. For GROUP BY d.name
with d.name AS dept, the group expression's column name was looked
up in {"dept","n","total"} and missed. FindColIdx returned 0, every
row got an empty group key, and the hash collapsed everything into
one bucket.
Fix: new FindGroupIdx walks aCols (SELECT list expressions) instead,
matching the GROUP BY column against each SELECT item's source
expression ND_COL name. Handles qualified refs (d.name -> NAME) and
falls back to FindColIdx for cases where GROUP BY uses a column not
in the SELECT list.
Also hoisted the resolution out of the per-row loop — GROUP BY
columns resolve once into aGroupIdx[] so each row just indexes.
Validation:
- FiveSql2 43/43
- Harbour compat 51/51
- Complex bench Q4: 1 row -> 100 rows (correct)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
FiveSql2 — SQL Engine for Harbour DBF/NTX/CDX
Pratt parser + SQL:1992-2023 full standard support Supports both NTX (Clipper) and CDX (FoxPro/ADS) indexes
Architecture
five_SQL("SELECT ...")
│
├── TSqlLexer Tokenizer
├── TSqlParser2 Pratt parser (data-driven operators)
├── TSqlExecutor Query executor (Volcano model)
│ ├── TSqlAlias Central alias manager (no collisions)
│ ├── TSqlIndex NTX/CDX index optimization (auto-detect)
│ ├── TSqlAgg GROUP BY / aggregation
│ ├── TSqlSort ORDER BY / DISTINCT
│ ├── TSqlDDL CREATE/DROP/ALTER TABLE/INDEX
│ └── TSqlTxn BEGIN/COMMIT/ROLLBACK
├── TSqlExpr AST nodes + expression evaluation
└── TSqlFunc 60+ scalar functions
Build & Test
export PATH="/path/to/harbour-core/bin/linux/gcc:$PATH"
export HB_INSTALL_PREFIX="/path/to/harbour-core"
make # Build all tests
make test # Run all 157 tests
make bench # Parser benchmark
make clean # Clean
SQL Standard Coverage
| Standard | Features | Tests |
|---|---|---|
| SQL:1992 | SELECT, JOIN, GROUP BY, HAVING, Subquery, CASE, CAST | 43 |
| SQL:1999 | CTE, Recursive CTE, Window Functions, MERGE | 10 |
| SQL:2003 | SIMILAR TO, GROUPING SETS, LATERAL, Window frames | 64 |
| SQL:2008 | FETCH/OFFSET, FOR UPDATE, Extended MERGE | (incl.) |
| SQL:2016 | JSON functions, LISTAGG | (incl.) |
| SQL:2023 | ANY_VALUE, GREATEST/LEAST, BOOL_AND/OR | (incl.) |
| Challenge | LeetCode-level complex queries | 15 |
| Extreme | Production analytics stress tests | 15 |
Adding New Operators
Edit TSqlParser2.prg, method InitInfixTables():
::hInfixTT[ TK_MYOP ] := { "<=>", 40, 41, ND_BIN }
One line. No structural changes needed.
Copyright
Copyright (c) 2025-2026 Charles KWON (Charles KWON OhJun) Email: charleskwonohjun@gmail.com All rights reserved.