CharlesKWON
67cd8f2306
Addresses two of the three layers behind the audit's "WorkArea
collision under multi-session" risk surfaced in Phase 3:
1. Shared DATA-INIT hash literals (PRG side).
TSqlSession.prg declared `DATA hPlanCache INIT { => }` (plus
hSavepoints + hRolePerms etc.). On the gengo path that
compiles class-DATA INITs, the {=>} literal is sometimes
evaluated ONCE at class-definition time, with every
subsequent New() reusing the same hash pointer. Two pgserver
connections then read/wrote a single shared HbHash from
different goroutines, eventually hitting `concurrent map
writes` inside HbHash.ensureIndex (the lazy O(1)-lookup
index map).
The pre-existing gotcha is already documented in
TSqlExecutor.prg's hSubCache comment ("DATA INIT on hash/
array literals can end up sharing the same instance across
New() calls depending on the compile path") — TSqlSession had
missed the same workaround. Moving the explicit
`::hPlanCache := { => }` etc. into the constructor body
guarantees a fresh hash per instance.
2. Stale cross-session recCount cache (Go side).
`*DBFArea.RecCount()` in shared mode caches its result for
the duration of `recCountCacheGen`. Append() bumped the count
on disk + refreshed THIS area's count under the append-intent
lock (Phase 1 of pre-1.0 audit) but never invalidated the
cache on peer DBFArea instances — so a second pgserver
connection's RecCount() kept returning its pre-Append cached
value. The peer's SELECT then iterated 1..old_count and
missed the newly inserted row.
Append() now calls `InvalidateRecCountCache()` after
committing the bumped header. The generation counter went
to atomic.AddUint64 / atomic.LoadUint64 so the bump is
safe to fire from any goroutine without a lock around the
variable.
Measured impact
---------------
Same 3-worker concurrent-INSERT-then-SELECT stress test that was
~3/5 passing pre-fix:
before: 3 / 5 (40% — plus occasional Go-level panic)
after: 8 / 10 (80% — no panics, just intermittent missed rows)
The remaining 20% flake is on the third layer — peer mmap shows a
pre-Append snapshot when Append's `unmap()` only invalidates this
area's own mmap, not the other workareas that opened the same DBF
file independently via dbUseArea. Fixing that requires either a
cross-area registry of mmap views to invalidate, or skipping
mmap entirely when SHARED && cache-gen has bumped. Tracked as a
proper follow-up; tests/pgserver/run.sh's "Known limitation"
header now points at the narrower problem.
Standalone six-gate verification:
go test ./... ✓
FiveSql2 SQL:1999 43/43 ✓
Harbour compat 56/56 ✓
std.ch 17/17 ✓
FRB 7/7 ✓
pgserver integration 6/6 ✓
Co-Authored-By: Claude Opus 4.7 (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.