---
title: "HeliosDB Nano v3.11.0 Release Notes"
---

# HeliosDB Nano v3.11.0 Release Notes

**Theme:** RAG-native primitives -- graph traversal, hybrid search, and MCP extensions

---

## Highlights

This release introduces a complete set of RAG (Retrieval-Augmented Generation) primitives directly into Nano's embedded engine. You can now do graph traversal, full-text BM25 search, vector similarity search, and rank-fusion -- all from SQL, in a single binary, with no external services.

---

## What's New

### Graph Engine

A lightweight in-memory graph layer with adjacency lists, exposed through SQL functions:

```sql
-- Traverse from a starting node, depth 2 across 'KNOWS' edges
SELECT * FROM graph_traverse(
  start_node => 'uuid-here',
  edge_label => 'KNOWS',
  direction  => 'OUT',
  depth      => 2
);

-- Shortest path with Dijkstra
SELECT * FROM graph_shortest_path(
  from_node => 'uuid-a',
  to_node   => 'uuid-b',
  algorithm => 'dijkstra'
);
```

Algorithms supported: BFS, Dijkstra, bidirectional BFS.

### Full-Text BM25 + Hybrid Search

```sql
-- Pure BM25 keyword search
SELECT * FROM documents
WHERE bm25_match(content, 'graph database for AI')
ORDER BY bm25_score(content, 'graph database for AI') DESC
LIMIT 10;

-- Hybrid: BM25 + vector with RRF fusion
SELECT * FROM hybrid_search(
  table_name   => 'documents',
  query_text   => 'graph database for AI',
  query_vector => embed('graph database for AI'),
  vector_column=> 'embedding',
  text_column  => 'content',
  fusion       => 'rrf',
  limit        => 20
);
```

Fusion strategies: RRF (Reciprocal Rank Fusion), MMR (Maximal Marginal Relevance), Linear.

### Compiled Query Plans

Frequently executed queries can be cached as compiled plans, skipping parser/planner overhead:

```sql
PREPARE COMPILED find_similar AS
  SELECT * FROM hybrid_search(
    table_name   => 'documents',
    query_vector => $1,
    vector_column=> 'embedding',
    text_column  => 'content',
    fusion       => 'rrf',
    limit        => 20
  );

EXECUTE find_similar(embed('my query'));
```

Plans are cached in an LRU and survive across connections within a process.

### MCP Server Extensions

6 new tools and 2 new resources for AI agents using Model Context Protocol:

**Tools:**
- `heliosdb_bm25_index` -- create BM25 indexes
- `heliosdb_hybrid_search` -- BM25+HNSW with RRF/MMR
- `heliosdb_graph_add_edge` -- add graph edges
- `heliosdb_graph_traverse` -- traverse from a node
- `heliosdb_graph_path` -- find shortest path
- `heliosdb_embed_and_store` -- vectorize text and INSERT in one call

**Resources:**
- `heliosdb://schema/{table}` -- schema introspection
- `heliosdb://stats/{table}` -- table statistics

### Performance: Arena Allocation (Internal)

A new `RequestArena` (built on `bumpalo::Bump`) is now available throughout the engine for per-request allocations. Hot paths in graph traversal and search use it to reduce allocator pressure under load. Application code generally does not need to interact with it directly.

---

## Known Limitations

- **Graph and BM25 storage are in-memory.** Persistence to RocksDB column families is planned for v3.12.0. For embedded use cases that rebuild the index on startup, this is fine; for long-lived deployments, persist source data to tables and warm graph/BM25 indexes on startup.
- **MCP extensions ship in `mcp_extensions` module.** The legacy `src/mcp/` server module is being migrated; in the meantime, new tools are accessed through the extensions module.

---

## Migration

No breaking changes. v3.11.0 is fully wire-compatible with v3.10.0.

To use the new SQL functions, no schema migration is required. The first `bm25_match` or `graph_traverse` call materializes the index on demand.

---

## Compatibility Matrix

| Component | Version |
|-----------|---------|
| PostgreSQL wire | 14, 15, 16 |
| MySQL wire | 5.7, 8.0 |
| Oracle wire | (subset) |
| MCP protocol | 1.0 |