Stoolap Files

What's New in v0.2.3

SmartString - Custom SSO String

• Inline storage for strings ≤22 bytes (no heap allocation)
• Owned (Box<str>) for computed values, Shared (Arc<str>) for cloned values
• 24-byte size with O(1) clone for shared variant

I64Map - High-Performance Hashmap for i64 Keys

• Uses i64::MIN as empty sentinel (row/txn IDs are always ≥0)
• FxHash-based with linear probing and backward-shift deletion
• ~45% faster lookups than FxHashMap<i64, V>

Value Interning

• Interned: NULL (all 7 DataTypes), booleans, integers 0-1000
• Reduces allocations for frequently used values in rows

Aggregation Fixes & Optimizations

• Fixed hash collision bug in single-column GROUP BY (was using hash as key)
• Added 2-column tuple optimization (30% faster than Vec<Value>)
• Single-column primitive GROUP BY uses I64Map directly

SIMD Pattern Matching

• memchr::memmem for LIKE '%pattern%' substring search
• Pre-compiled Finder stored in CompiledPattern

O(1) COUNT(*) and COUNT(DISTINCT) Fast Paths

• Committed row count atomic counter for O(1) COUNT(*)
• get_distinct_count_excluding_null() in Index trait for O(1) COUNT(DISTINCT)
• Compiled query cache for COUNT queries with schema epoch validation
• Performance: COUNT(*) ~22.5µs → ~2.9µs (7.7x faster)

Background Cleanup and Memory Management

• Background cleanup thread for periodic garbage collection
• Configurable via CleanupConfig (interval, retention periods)
• Arena slot reuse to prevent unbounded memory growth
• Memory at program end: 665 KB → 153.6 KB (77% reduction)

Global Pool and Cache Cleanup

• clear_version_map_pools() for TransactionVersions pools
• clear_program_cache() for expression bytecode LRU cache
• clear_classification_cache() for query classification LRU cache

Other Improvements

• CompactVec: new insert(), retain(), drain() methods
• All indexes migrated to I64Map and CompactVec
• Index trait _into methods to avoid allocations
• RowIdVec pooled vector for index lookups (256K max cached capacity)
• BTree index optimization using Borrow trait for lookups
• Thorough SAFETY documentation on unsafe code

Full Changelog: https://github.com/stoolap/stoolap/compare/v0.2.2...v0.2.3