CharlesKWON
7babfb7281
Systematic bug-hunt driven by an automated analysis of all FiveSql2 source files. Each fix is targeted — no speculative refactoring. --- #1 CLASSDATA hSubCache leaked across queries (CRITICAL) --- CLASSDATA hSubCache INIT { => } SHARED shared one hash across ALL TSqlExecutor instances. A non-correlated subquery cached in query A was silently returned for an unrelated query B if the subquery text happened to produce the same cache key. Converted to instance DATA initialized in New(). --- #5+#21 IS NULL / COALESCE treated empty string as NULL (HIGH) --- RETURN xL == NIL .OR. ( ValType(xL) == "C" .AND. Empty(AllTrim(xL)) ) SQL standard: '' is a valid non-NULL value. Removed the empty-string check from both IS NULL evaluation and COALESCE skip logic. --- #4 Multiple ? parameters all returned first value (HIGH) --- ND_PAR nodes had no index — EvalExpr always returned ::aParams[1]. Parser now stamps each ? with a sequential 1-based index in xNode[2]. EvalExpr uses it to return the correct ::aParams[n]. --- #10+#11 SqlEvalRowExpr missing / and || operators, single-arg function eval (MEDIUM) --- Division and string concatenation fell through to RETURN NIL in the row-expression evaluator used by recursive CTEs and aggregate ComputeAgg. Also, multi-argument functions like SUBSTR(x,2,3) only received the first argument. Both fixed. --- #9 SUM/AVG/MIN/MAX of all NULLs returned 0 instead of NULL (MEDIUM) --- SQL standard requires NULL. Changed the aggregate return path to return NIL when nCount == 0 (SUM/AVG) or when xMin/xMax == NIL. --- #8 MIN/MAX used SqlCoerceNum for comparison (MEDIUM) --- Strings and dates were coerced to numbers (Val()) before comparing, making MIN('banana') == MIN('apple') == 0. Switched to SqlCmpLt which handles type-appropriate comparison. --- #7 SqlExprHasAgg only checked top-level node (MEDIUM) --- Expressions like `salary + COUNT(*)` were not detected as containing an aggregate because the top node was ND_BIN, not ND_FN. Made the function recursive — walks ND_BIN, ND_UNI, ND_FN args, ND_CASE branches. --- #13 SELECT * only expanded first table in JOINs (MEDIUM) --- `SELECT * FROM orders o JOIN customers c ON ...` only included fields from orders. Changed the expansion loop to iterate ALL entries in ::aTables. --- #2 s_aOuterStack not unwound on subquery error (HIGH) --- SubqueryCached's PushOuter/PopOuter pair was not protected by BEGIN SEQUENCE. A runtime error inside the subquery left a stale entry on the module-level outer stack, corrupting all subsequent queries' correlated column resolution. Wrapped in SEQUENCE/RECOVER. Validation: - FiveSql2 43/43 - Harbour compat 51/51 - go test ./... ALL PASS 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.