HeliosDB-Lite v3.6.0 Release Notes

Release Date: March 2026

Headline

v3.6.0 is the largest feature release in HeliosDB-Lite history, adding 22 previously internal-only features to the SQL interface, comprehensive database hardening, and a 129x query performance improvement via plan caching.

Performance

Plan Cache: 129x average speedup on repeated queries (skip parse/plan/optimize)
vs PostgreSQL 16: 33 of 35 benchmark categories won (up from 34/35 in v3.5)
REFRESH MATVIEW: Flipped from PostgreSQL win (5.8x) to Helios win (1,279x)

New SQL Commands

Command	Description
`BACKUP DATABASE [INCREMENTAL] [TO '<path>']`	COW incremental-forever backup
`RESTORE DATABASE FROM '<id>' [TO BRANCH '<name>']`	Restore with chain walking
`RECOVER DATABASE TO TIMESTAMP '<ts>' [AS BRANCH '<name>']`	Point-in-time recovery with branch forking
`VACUUM [FULL] [ANALYZE] [table]`	MVCC version cleanup + statistics
`CHECKPOINT [FORCE]`	WAL flush and rotation
`REINDEX TABLE/INDEX`	Force index rebuild
`ALTER TABLE ENABLE/DISABLE ROW LEVEL SECURITY`	RLS toggle
`CREATE/DROP POLICY`	Row-level security policies
`CREATE ROLE WITH RATE_LIMIT <rpm>`	Per-user rate limiting
`CREATE ROLE WITH SSL_REQUIRED`	Connection-level SSL enforcement
`ALTER SYSTEM ROTATE ENCRYPTION KEY`	Encryption key rotation
`ALTER TABLE ENABLE/DISABLE ZERO KNOWLEDGE ENCRYPTION`	Per-table ZKE
`ALTER COLUMN SET COMPRESSION zstd/lz4/none`	Per-column compression
`ALTER MATERIALIZED VIEW SET (refresh_interval='5m')`	MV auto-refresh scheduling
`CREATE/DROP EXTENSION FROM '<path>'`	WASM plugin management
`CREATE/DROP PUBLICATION/SUBSCRIPTION`	Logical replication (feature-gated)
`CONSOLIDATE FILTER [table]`	SMFI rebuild
`GRANT role TO user`	Role hierarchy via custom parser

New SQL Functions

Function	Description
`pg_cancel_backend(pid)`	Cancel a running query
`pg_terminate_backend(pid)`	Terminate a session
`pg_backend_pid()`	Get current process ID
`%` (modulo operator)	Integer and float modulo

New System Views (22 views added, 94 total)

View	Category
`helios_dictionary`	Lists all 94 system views (Oracle DICT equivalent)
`helios_audit_log`	Tamper-proof audit trail
`helios_bloom_filters`	Bloom filter statistics
`helios_zone_maps`	Zone map min/max statistics
`helios_resource_usage`	HTAP quota monitoring
`helios_index_stats`	Index metadata
`helios_advisor_recommendations`	Workload advisor output
`pg_stats`	PG-compatible column statistics
`helios_dedup_stats`	Content-addressed dedup ratios
`helios_prefetch_stats`	Prefetch cache stats
`helios_smfi_status`	Self-maintaining filter status
`helios_encryption_keys`	Key rotation history
`helios_zke_status`	ZKE per-table status
`helios_mv_refresh_status`	MV auto-refresh schedule
`helios_column_compression`	Per-column codec
`pg_publications`	Logical replication publications
`pg_subscriptions`	Logical replication subscriptions
`helios_extensions`	WASM plugin registry
`helios_graphql_status`	GraphQL gateway status
`helios_circuit_breaker_status`	Circuit breaker config
`helios_backups`	Backup metadata catalog
`helios_user_quotas`	Rate limit quota tracking

Security Hardening

PBKDF2: 100,000 iterations (was 4,096)
Resource limits: max_result_rows (1M), CTE depth (1000), subquery depth (64), expression depth (128), memory per query
CRC32 checksums: Opt-in data integrity verification
PRAGMA integrity_check: Full data corruption scan
API validation: SQL size (1MB), param count (64K), timeout bounds
PostgREST: Refactored to parameterized queries (SQL injection eliminated)

PL/pgSQL Enhancements

FOR loops (numeric + query)
WHILE loops
CASE (searched + simple)
Cursors (OPEN/FETCH/CLOSE)
EXIT/CONTINUE
SELECT INTO
EXECUTE (dynamic SQL)

Optimizer

Rules split into 8 focused modules (was 2,712-line monolith)
All panic!() replaced with proper error propagation
FilteredScan CTE conflict resolved

Repository Organization

README.md at repo root
24 test files renamed to standard convention
docs/FEATURE_FLAGS.md documenting 47 Cargo features
READMEs for examples/, sdks/, integrations/, benches/
Stale files cleaned, .gitignore updated

Graph Adjacency Lists (New)

Property graph layer with DashMap-based concurrent adjacency lists:

Nodes: 64-bit ID with optional label and properties
Edges: Directed, typed, optionally weighted
Traversal: BFS, Dijkstra shortest path, A* with pluggable heuristic
SQL functions: graph_bfs(), graph_shortest_path(), graph_a_star(), graph_neighbors() (declared; wiring pending storage backend integration)

BM25 & Hybrid Search (New)

RAG-native lexical and hybrid search:

BM25 inverted index with Okapi parameters (k1=1.2, b=0.75)
Unicode-aware tokenizer with ASCII folding
Hybrid search: weighted linear combination or Reciprocal Rank Fusion (RRF)
Rerankers: RRF (Cormack/Clarke 2009, k=60) and Maximal Marginal Relevance (MMR)
Bloom filter skip: short-circuit term lookups for non-existent terms

Arena Allocation (New)

Per-request bump allocator (bumpalo-based):

Zero-cost deallocation (drop whole arena)
16 KiB default initial capacity
Telemetry: bytes_allocated(), chunk_count()
Reusable across requests for warmed memory

Compiled Query Plans (New)

PlanFingerprint: stable hash of normalized SQL (comments stripped, literals replaced)
CompiledPlan: parsed + validated prepared statement with parameter slots
PlanCache: bounded LRU (512 entries), thread-safe

Production Hardening (New)

Feature	Description
FK constraint enforcement	INSERT/UPDATE/DELETE validate foreign keys
MVCC GC background thread	5-minute interval, 1-hour retention window
Backup snapshot consistency	Single-pass scan for consistent snapshots
Index error escalation	PK/UNIQUE violations return ERROR, not warning
NaN/Infinity guards	Aggregate functions reject NaN/Infinity
SQL cursors	DECLARE/FETCH/CLOSE for streaming result sets
Connection management	Timeouts, idle disconnect, rollback on disconnect
DDL locking	RwLock for schema operations
/metrics endpoint	Prometheus-compatible metrics
/health endpoint	Health check (HTTP 200 + JSON)
SET TRANSACTION ISOLATION LEVEL	Runtime isolation level control
Adaptive timeout sampling	1000 to 100 row sampling

Breaking Changes

None. All changes are additive.

Test Coverage

1,502+ lib tests, 0 failures
58+ E2E feature tests covering every user-facing feature
19 tutorials in Docs-Public/Lite/docs/tutorials/