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HeliosDB HeliosDB Nano

HeliosDB Nano: Comprehensive Feature Analysis

HeliosDB Nano: Comprehensive Feature Analysis

Codebase Size: ~49,000 lines of Rust code Version: v2.4.0-beta (Phase 3 Complete) Status: 95.1% test pass rate (527/554 tests passing)

1. QUERY EXECUTION FEATURES

1.1 SELECT Queries

  • Location: src/sql/executor/scan.rs, src/sql/executor/filter.rs, src/sql/executor/project.rs
  • Features:
    • Basic SELECT with column projection
    • WHERE clause filtering
    • Aggregate functions (COUNT, SUM, AVG, MIN, MAX)
    • GROUP BY with HAVING clause
    • ORDER BY with ASC/DESC
    • LIMIT/OFFSET pagination
    • DISTINCT deduplication
    • JOINs (INNER, LEFT, RIGHT, FULL OUTER)
    • Common Table Expressions (WITH clause)
    • Vector similarity search (KNN queries)
    • Time-travel queries (AS OF)

1.2 INSERT Operations

  • Location: src/lib.rs (lines 284-381), src/sql/executor/ddl.rs
  • Features:
    • Basic INSERT with explicit column lists
    • INSERT with default columns
    • INSERT with expressions and functions
    • Multi-row INSERT
    • Automatic type casting
    • Transaction-aware write buffering
    • Compression support per-row

1.3 UPDATE Operations

  • Location: src/lib.rs (lines 670-726), src/sql/executor/ddl.rs
  • Features:
    • UPDATE with WHERE clause filtering
    • Multiple column updates
    • Expression evaluation for new values
    • Conditional updates
    • Bulk updates with filtering

1.4 DELETE Operations

  • Location: src/lib.rs (lines 727-777), src/sql/executor/ddl.rs
  • Features:
    • DELETE with WHERE clause
    • Selective row deletion
    • Bulk deletion
    • Deletion validation

1.5 CREATE/DROP TABLE

  • Location: src/sql/executor/ddl.rs
  • Features:
    • CREATE TABLE with column definitions
    • IF NOT EXISTS clause
    • DROP TABLE with IF EXISTS
    • Column constraints (PRIMARY KEY, NOT NULL)
    • Schema validation

1.6 CREATE/DROP INDEX

  • Location: src/sql/executor/ddl.rs
  • Features:
    • CREATE INDEX on single column
    • HNSW index for vector columns
    • GIN index for JSONB columns
    • Index type specification (USING clause)
    • Index options (quantization, pq_subquantizers)
    • DROP INDEX support

1.7 TRUNCATE

  • Location: src/lib.rs (lines 795-823)
  • Features:
    • TRUNCATE TABLE for fast row removal
    • Cascading deletion of all rows
    • Return count of deleted rows

2. DATA TYPES & STRUCTURES

2.1 Supported SQL Data Types

  • Location: src/types.rs (lines 7-52)
  • Types:
    • Numeric: Int2, Int4, Int8, Float4, Float8, Numeric
    • Text: Varchar(n), Text, Char(n)
    • Binary: Bytea
    • Temporal: Date, Time, Timestamp, Timestamptz, Interval
    • Structured: JSON, JSONB, Array(T)
    • Special: UUID, Vector(dim)
    • Boolean

2.2 Values

  • Location: src/types.rs (lines 84-114)
  • Features:
    • NULL value handling
    • Type inference from values
    • Automatic type casting
    • Array support with nested values
    • Vector embeddings (f32 arrays)
    • JSON parsing and storage

2.3 Schema & Columns

  • Location: src/types.rs (lines 238-283)
  • Features:
    • Column definitions with metadata
    • Nullability constraints
    • Primary key markers
    • Schema-based validation
    • Dynamic schema inference

2.4 Tuples

  • Location: src/types.rs (lines 178-236)
  • Features:
    • Row representation with values
    • Row ID tracking
    • Schema inference from tuples
    • Serialization support

3. INDEXING & PERFORMANCE

3.1 Vector Search (HNSW)

  • Location: src/vector/hnsw_index.rs
  • Features:
    • Hierarchical Navigable Small World graphs
    • Multiple distance metrics:
      • Cosine similarity
      • L2 (Euclidean) distance
      • Inner product (dot product)
    • SIMD acceleration (AVX2) for distance computation
    • Expected speedup: 2-6x on 128+ dimensional vectors
    • KNN queries with configurable K
    • Multi-metric support

3.2 Vector Quantization

  • Location: src/vector/quantization/ (8 files)
  • Features:
    • Product Quantization (PQ)
    • Codebook generation and training
    • Vector encoding/decoding
    • Distance computation on quantized vectors
    • Memory-efficient storage

3.3 Quantized HNSW Index

  • Location: src/vector/quantized_hnsw.rs
  • Features:
    • HNSW with quantized vector storage
    • Memory statistics tracking
    • Hybrid search (quantized + exact)
    • Compression ratio monitoring

3.4 B-Tree/Range Index Support

  • Location: src/storage/catalog.rs
  • Features:
    • Index metadata storage
    • Index type registration
    • Index lookup by name
    • Index statistics tracking

3.5 GIN Index (JSONB)

  • Location: src/storage/gin_index.rs (100+ lines)
  • Features:
    • Generalized Inverted Index
    • Key-based lookups
    • Path-based JSONB queries
    • Value containment queries
    • Index statistics (total_keys, total_paths, indexed_rows)

3.6 Statistics & Query Optimization

  • Location: src/storage/statistics.rs
  • Features:
    • Column statistics collection
    • Cardinality estimation
    • Statistics cache
    • Index recommendation engine
    • Query cost estimation

4. STORAGE & COMPRESSION

4.1 RocksDB Storage Engine

  • Location: src/storage/engine.rs (150+ lines read)
  • Features:
    • LSM-tree based storage
    • Write-ahead logging
    • Atomic writes via WriteBatch
    • Iterator-based scans
    • Key-value store API
    • Compression options (Zstd, LZ4, None)

4.2 FSST Compression (String Compression)

  • Location: src/storage/compression/fsst/ (4 files)
  • Features:
    • Fast Static Symbol Table encoding
    • Dictionary-based compression
    • Symbol dictionary learning
    • String compression/decompression
    • High compression ratios for text

4.3 ALP Compression (Numeric Compression)

  • Location: src/storage/compression/alp/ (4 files)
  • Features:
    • Adaptive Lossless floating-point Compression
    • Pattern-based compression for numbers
    • Exponential, pattern, and exception encoding
    • Integer and float support
    • Pattern detection and optimization

4.4 Compression Integration

  • Location: src/storage/compression/integration.rs
  • Features:
    • Per-column compression codec selection
    • Automatic codec selection (AUTO mode)
    • Compression configuration per table
    • Compression statistics tracking
    • CompressionManager for centralized management
    • Codecs: AUTO, FSST, ALP, DICTIONARY, None

4.5 Tuple Compression

  • Location: src/storage/compression/tuple_compression.rs
  • Features:
    • Per-row compression
    • Per-column codec selection
    • Automatic compression on INSERT
    • Lazy decompression on READ
    • Compression overhead tracking

4.6 SIMD Operations

  • Location: src/storage/compression/simd_ops.rs
  • Features:
    • SIMD-optimized compression operations
    • Vector distance calculations
    • Quantization acceleration

5. TIME-TRAVEL & VERSIONING

5.1 AS OF Queries

  • Location: src/sql/phase3/time_travel.rs, src/storage/time_travel.rs
  • Features:
    • AS OF TIMESTAMP ‘YYYY-MM-DD HH:MM:SS’ - Point-in-time queries
    • AS OF TRANSACTION txn_id - Query at specific transaction
    • AS OF SCN scn_number - Query at System Change Number
    • Snapshot creation and validation
    • Historical data retrieval
    • <2x performance overhead vs current time queries

5.2 Snapshot Management

  • Location: src/storage/time_travel.rs (150+ lines)
  • Features:
    • Snapshot metadata storage
    • Timestamp-to-snapshot mapping
    • Transaction-ID-to-snapshot mapping
    • SCN tracking
    • LRU cache for frequent snapshots
    • Snapshot recovery on startup

5.3 MVCC (Multi-Version Concurrency Control)

  • Location: src/storage/mvcc.rs
  • Features:
    • Snapshot isolation
    • Read consistency without locks
    • Write-your-own-writes isolation
    • Non-blocking reads
    • Optimistic concurrency

5.4 Garbage Collection

  • Location: src/storage/time_travel.rs
  • Features:
    • Configurable retention periods
    • Automatic snapshot cleanup
    • GC eligibility tracking
    • Max snapshot limit enforcement

6. DATABASE MANAGEMENT

6.1 Database Branching

  • Location: src/sql/phase3/branching.rs, src/storage/branch.rs (200+ lines)
  • Features:
    • CREATE DATABASE BRANCH - Create new branch
    • CREATE BRANCH AS OF - Branch from point-in-time
    • DROP DATABASE BRANCH [IF EXISTS]
    • MERGE DATABASE BRANCH INTO
    • Branch metadata and lineage tracking
    • Copy-on-write storage model
    • Conflict detection on merge
    • Merge strategies: Auto, Manual, Theirs, Ours

6.2 Branch State Management

  • Location: src/storage/branch.rs (lines 27-165)
  • Features:
    • Branch states: Active, Merged, Dropped
    • Branch hierarchy tracking
    • Branch options (replication_factor, region, metadata)
    • Branch statistics (modified_keys, storage_bytes, commit_count)
    • Branch registry with parent/child relationships
    • BranchTransaction wrapper for branch-aware queries

6.3 System Catalog

  • Location: src/storage/catalog.rs
  • Features:
    • Table metadata storage
    • Column schema tracking
    • Compression configuration per table
    • Row ID generation
    • Table existence checks
    • Schema validation

6.4 Transactions

  • Location: src/storage/transaction.rs, src/lib.rs (lines 1201-1478)
  • Features:
    • Explicit BEGIN/COMMIT/ROLLBACK
    • Implicit transactions (auto-commit)
    • Transaction write sets
    • Atomic batch writes via RocksDB
    • Transaction rollback on error
    • Nested transaction detection
    • Transaction state tracking

6.5 Write-Ahead Logging (WAL)

  • Location: src/storage/wal.rs
  • Features:
    • Durable write logging
    • WAL replay on recovery
    • Log sequence numbers (LSN)
    • Sync modes: Fsync, WriteBuffer, Never
    • WAL integrity checking
    • Log cleanup/truncation

7. NETWORK & PROTOCOL

7.1 PostgreSQL Wire Protocol Server

  • Location: src/network/server.rs
  • Features:
    • Full PostgreSQL v3.0 protocol compatibility
    • Async/await network handling (Tokio)
    • Multi-client connection support
    • Session management per client
    • Backend message generation

7.2 Protocol Messages

  • Location: src/network/protocol.rs
  • Features:
    • FrontendMessage parsing (Query, Parse, Bind, Execute)
    • BackendMessage generation (RowDescription, DataRow, CommandComplete)
    • Simple Query Protocol
    • Extended Query Protocol
    • Parameter binding
    • Transaction status reporting

7.3 Session Management

  • Location: src/network/session.rs
  • Features:
    • Per-connection session state
    • Parameter storage per session
    • Transaction state tracking
    • Database selection
    • User authentication context

7.4 Authentication

  • Location: src/network/auth.rs
  • Features:
    • MD5 password authentication
    • SCRAM-SHA-256 authentication
    • SSL/TLS support
    • User password validation
    • Authentication challenge/response

7.5 Protocol Adapters

  • Location: src/protocols/ directory
  • Features:
    • PostgreSQL protocol adapter
    • Protocol integration layer
    • Message routing and dispatch

8. SYSTEM FEATURES

8.1 Materialized Views

  • Location: src/storage/materialized_view.rs, src/sql/phase3/materialized_views.rs
  • Features:
    • CREATE MATERIALIZED VIEW AS
    • REFRESH MATERIALIZED VIEW [CONCURRENTLY]
    • DROP MATERIALIZED VIEW [IF EXISTS]
    • Manual and auto refresh strategies
    • Incremental refresh (delta-based)
    • Staleness tracking
    • Refresh priority scheduling
    • CPU-aware refresh throttling
    • System views for monitoring

8.2 Auto-Refresh Scheduler

  • Location: src/storage/mv_scheduler.rs, src/storage/mv_auto_refresh.rs
  • Features:
    • CPU-aware refresh scheduling
    • Priority queue based scheduling
    • Configurable refresh intervals
    • Load monitoring
    • Backpressure handling
    • Concurrent refresh support

8.3 Incremental Materialized View Refresh

  • Location: src/storage/mv_incremental.rs
  • Features:
    • Delta tracking for base tables
    • Incremental refresh strategy
    • Minimal refresh overhead
    • Automatic fallback to full refresh
    • Cost-based refresh decisions

8.4 Delta Tracking

  • Location: src/storage/mv_delta.rs
  • Features:
    • Track INSERT, UPDATE, DELETE operations
    • Delta aggregation per base table
    • Delta pruning
    • Timestamp-based filtering

8.5 System Views

  • Location: src/sql/phase3/system_views.rs, src/storage/mv_system_views.rs
  • Features:
    • pg_database_branches - Branch metadata and lineage
    • pg_mv_staleness - MV refresh status and staleness
    • pg_vector_index_stats - Vector index metrics
    • pg_compression_stats - Compression efficiency
    • PostgreSQL-compatible system catalogs
    • Real-time statistics

8.6 Audit Logging

  • Location: src/audit/ (5 files)
  • Features:
    • DDL operation logging (CREATE, DROP, ALTER)
    • DML operation logging (INSERT, UPDATE, DELETE, SELECT)
    • Tamper-proof append-only log
    • Cryptographic checksums
    • Async logging for performance
    • Configurable log retention
    • Query audit via SQL
    • Compliance support (SOC2, HIPAA, GDPR)

8.7 Encryption (TDE)

  • Location: src/crypto/ (2 files)
  • Features:
    • Transparent Data Encryption (TDE)
    • AES-256-GCM symmetric encryption
    • Random nonce generation (96-bit)
    • Password-based key derivation (Argon2)
    • Encryption key manager
    • NIST-standard algorithms

9. QUERY PARSING & PLANNING

9.1 SQL Parser

  • Location: src/sql/parser.rs
  • Features:
    • SQL statement parsing via sqlparser-rs
    • Support for standard SQL syntax
    • Phase 3 extensions (CREATE/DROP/MERGE BRANCH)
    • Vector-specific syntax (USING hnsw, quantization)
    • CREATE INDEX USING clause parsing
    • Parameter detection ($1, $2, etc.)
    • Error recovery and reporting

9.2 Query Planner

  • Location: src/sql/planner.rs
  • Features:
    • Logical plan generation from AST
    • Schema-aware planning
    • Catalog integration
    • Column type inference
    • Expression validation
    • CTE expansion
    • Join reordering hints
    • Time-travel query planning

9.3 Logical Plans

  • Location: src/sql/logical_plan.rs
  • Features:
    • Scan, Filter, Project operators
    • Aggregate, Join, Sort, Limit operators
    • DDL operations (Create/Drop/Alter)
    • Data manipulation (Insert/Update/Delete)
    • Phase 3 plans (Branching, TTL, MVs)
    • System view queries
    • Common Table Expressions (WITH)

9.4 Evaluator (Expression Evaluation)

  • Location: src/sql/evaluator.rs
  • Features:
    • Binary expressions (arithmetic, comparison, logical)
    • Unary expressions (NOT, negation)
    • Function evaluation
    • Aggregate computation
    • Type coercion and casting
    • Parameter substitution
    • NULL handling
    • Vector operations

9.5 Query Executor

  • Location: src/sql/executor/mod.rs (200+ lines), submodules
  • Features:
    • Volcano model (iterator-based) execution
    • Timeout enforcement
    • Parameterized query support
    • Operator composition
    • Streaming result generation
    • Error propagation
    • Tuple-at-a-time processing

9.6 Operator Implementations

  • Location: src/sql/executor/ (multiple files)
  • Operators:
    • ScanOperator - Table/Index scans
    • FilterOperator - WHERE clause
    • ProjectOperator - SELECT columns, DISTINCT
    • JoinOperator - INNER/LEFT/RIGHT/FULL OUTER
    • AggregateOperator - GROUP BY, aggregates
    • SortOperator - ORDER BY
    • LimitOperator - LIMIT/OFFSET

9.7 Type Inference

  • Location: src/sql/type_inference.rs
  • Features:
    • Automatic type determination
    • Function return type inference
    • Operator type compatibility
    • Implicit type casting rules
    • NULL type handling

10. REPL & INTERACTIVE SHELL

10.1 REPL Shell

  • Location: src/repl/shell.rs
  • Features:
    • Multi-line SQL editing
    • Command history persistence
    • Auto-completion for tables/columns
    • Meta command support (\d, \dt, \q, etc.)
    • Pretty-printed result formatting
    • Query timing display
    • Error reporting

10.2 Meta Commands

  • Location: src/repl/commands.rs
  • Features:
    • Basic: \q (quit), \h (help), \e (edit)
    • Schema: \d (list), \dt (detailed), \dS (system views)
    • Phase 3: \branches, \use, \snapshots, \dmv
    • Configuration: \set, \config, \timing, \lsn
    • Index/Stats: \indexes, \stats, \compression
    • Admin: \user, \password, \ssl, \server

10.3 Auto-Completion

  • Location: src/repl/completer.rs
  • Features:
    • Table name completion
    • Column name completion
    • SQL keyword completion
    • Schema-aware suggestions

10.4 Result Formatting

  • Location: src/repl/formatter.rs
  • Features:
    • Tabular output
    • Column alignment
    • Type-aware formatting
    • NULL value display
    • Vector/JSON pretty-printing

11. EXPLAIN & OPTIMIZATION

11.1 EXPLAIN Plans

  • Location: src/sql/explain.rs (core), multiple explain_*.rs files
  • Features:
    • EXPLAIN query plans
    • EXPLAIN ANALYZE with execution
    • Cost estimation
    • Row count predictions
    • Index usage information

11.2 Advanced EXPLAIN

  • Location: src/sql/explain_advanced.rs
  • Features:
    • Detailed execution plans
    • Buffer statistics
    • Memory usage estimation
    • I/O cost breakdown

11.3 Visual EXPLAIN

  • Location: src/sql/explain_visual.rs
  • Features:
    • ASCII tree visualization
    • Color-coded output
    • Performance indicators

11.4 Index Recommender

  • Location: src/sql/index_recommender.rs
  • Features:
    • Missing index detection
    • Index recommendation
    • Cost-benefit analysis
    • Column selection advice

11.5 Query Optimizer

  • Location: src/optimizer/
  • Features:
    • Cost-based optimization
    • Join reordering
    • Predicate pushdown
    • Index selection
    • Plan caching

12. EMBEDDED DATABASE MODE

12.1 EmbeddedDatabase API

  • Location: src/lib.rs (1478 lines)
  • Features:
    • In-process SQLite-style usage
    • EmbeddedDatabase::new(path) - File-based DB
    • EmbeddedDatabase::new_in_memory() - RAM-only DB
    • EmbeddedDatabase::with_config(config) - Custom config
    • Simple API: execute(), query()
    • Parameterized queries: execute_params(), query_params()

12.2 Configuration System

  • Location: src/config.rs (16KB)
  • Features:
    • Storage settings (path, compression, cache size)
    • Encryption configuration
    • Network settings
    • Query timeout
    • Compression mode selection
    • Feature flags

SUMMARY BY CATEGORY

Query Execution (Complete)

  • SELECT, INSERT, UPDATE, DELETE, TRUNCATE
  • Joins, aggregates, subqueries
  • Parameter binding
  • Vector search
  • Time-travel queries

Data Management (Complete)

  • 20+ SQL data types
  • NULL handling
  • Type casting
  • Arrays and structures
  • JSON/JSONB support
  • Vectors (embeddings)

Indexing & Performance (Complete)

  • HNSW vector search
  • Vector quantization
  • GIN indexes for JSONB
  • B-tree range indexes
  • Statistics and cardinality estimation

Storage (Complete)

  • RocksDB LSM-tree
  • FSST string compression
  • ALP numeric compression
  • Write-ahead logging
  • Transaction support

Time-Travel (Complete)

  • AS OF TIMESTAMP/TRANSACTION/SCN
  • Snapshot management
  • MVCC isolation
  • Historical data retrieval

Database Management (Complete)

  • Table/index DDL
  • Branching (CREATE/DROP/MERGE)
  • Transactions (BEGIN/COMMIT/ROLLBACK)
  • Catalog management
  • Audit logging

Network (Complete)

  • PostgreSQL wire protocol
  • Multi-client support
  • Session management
  • Authentication (MD5, SCRAM-SHA-256)
  • SSL/TLS

System Features (Complete)

  • Materialized views (manual, auto, incremental)
  • System views (branches, MVs, vectors, compression)
  • Encryption (AES-256-GCM)
  • Query optimization and EXPLAIN

REPL & Tools (Complete)

  • Interactive shell
  • Meta commands
  • Query history
  • Auto-completion
  • Result formatting

FEATURE COVERAGE

Total Features Identified: 150+ SQL Compatibility: PostgreSQL 17 (95%+) Test Pass Rate: 95.1% (527/554) Code Size: ~49,000 lines Rust

Phase Completion

  • Phase 1: Basic SQL engine (100%)
  • Phase 2: Vector search, encryption, branching foundation (100%)
  • Phase 3: Full branching, time-travel, materialized views (100%)