minigdb

An embedded property-graph database built in Rust on RocksDB. Property graph model (nodes and edges with labels and key-value properties), ACID-compliant RocksDB-backed storage, and a GQL (ISO/IEC 39075) query language subset — usable as a REPL, a network server, or an embedded Rust/Python library.

Feature highlights:

• GQL queries: MATCH, INSERT, SET, DELETE, variable-length paths, OPTIONAL MATCH, UNION, aggregates, WITH, UNWIND
• 15 built-in graph algorithms: PageRank, shortest path, community detection (Louvain/Leiden), centrality measures, max-flow, and more
• Property indexes, uniqueness and type constraints, parameterized queries, CSV bulk import
• Multi-graph support, explicit transactions
• TCP server with authentication, per-connection transaction isolation, and an embedded web GUI
• Python bindings via PyO3 with polars/pandas DataFrame output

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Quick Start

Requires Rust (install via rustup).

# Build and launch the interactive REPL
cargo run

# Or build first, then run the binary directly
cargo build
./target/debug/minigdb

# Run the test suite
cargo test

Data is stored in the platform user-data directory:

Platform	Path
Linux	~/.local/share/minigdb/
macOS	~/Library/Application Support/minigdb/
Windows	%AppData%\minigdb\

The REPL prints the active data directory on startup. Each named graph gets its own graphs/<name>/ subfolder.

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REPL

The REPL auto-detects complete statements, so semicolons are optional. Multi-line input is supported; the prompt shows -> until the statement is complete (or txn-> inside a transaction). Input history is saved to .minigdb_history in the current directory.

Meta-commands

Command	Effect
:graphs	List all graphs, marking the active one
:create <name>	Create a new named graph and switch to it
:use <name>	Checkpoint the current graph and switch to an existing one
:drop <name>	Permanently delete a named graph
:checkpoint	Force a snapshot and truncate the WAL immediately
:quit or :q	Exit (writes a final checkpoint)
Ctrl-C	Cancel the current input line
Ctrl-D	Exit

Graph management commands are not allowed inside a BEGIN transaction.

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Example queries

INSERT (:Person {name: "Alice", age: 30})
INSERT (:Person {name: "Bob",   age: 25})
MATCH (a:Person {name: "Alice"}), (b:Person {name: "Bob"})
INSERT (a)-[:KNOWS]->(b)

MATCH (a)-[:KNOWS]->(b) RETURN a.name, b.name
CALL pageRank() YIELD node, score RETURN node, score ORDER BY score DESC

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Documentation

Topic	Description
Query Language	Full GQL reference: INSERT, MATCH, WHERE, aggregates, path quantifiers, indexes, constraints, transactions
Graph Algorithms	15 algorithms invoked via CALL … YIELD: PageRank, shortest path, centrality, community detection, max-flow
Network Server	TCP server, authentication, web GUI, wire protocol, HTTP API
Python API	Installation, local/remote usage, DataFrame output, parameterized queries, CSV import

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Storage

Each named graph is stored in its own graphs/<name>/ subdirectory, backed by RocksDB using eight column families:

Column Family	Contents
nodes	Node records (ID → bincode-serialized Node)
edges	Edge records (ID → bincode-serialized Edge)
adj_out	Outgoing adjacency index
adj_in	Incoming adjacency index
label_idx	Label → node ID set
edge_label_idx	Edge label → edge ID set
prop_idx	Property index (label + key + encoded value → node ID set)
meta	Graph metadata (index definitions, constraint definitions)

RocksDB provides atomic writes via WriteBatch, crash recovery via SST compaction, and supports graphs that exceed available RAM through its internal block cache.

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Architecture

src/
├── main.rs           # REPL (rustyline, graph management commands, server entry points)
├── lib.rs            # Public API and re-exports
├── gql.pest          # PEG grammar (pest, read at compile time)
├── python.rs         # Python bindings (PyO3, feature = "python")
├── csv_import.rs     # CSV bulk import
├── types/            # Value, NodeId (ULID), EdgeId (ULID), Node, Edge, DbError
├── graph/            # Graph struct + RocksDB-backed mutation helpers (ops.rs, constraints.rs)
├── storage/          # RocksStore (8 CFs), StorageManager, apply_ops replay helper
├── transaction/      # Operation enum (WAL replay units)
├── algorithms/       # 15 graph algorithm modules dispatched via CALL
├── query/            # AST, pest parser, tree-walking executor
└── server/
    ├── mod.rs        # Async TCP server, auth handshake, per-connection state
    ├── auth.rs       # ServerConfig, UserEntry, SHA-256 password hashing
    ├── registry.rs   # GraphRegistry — lazy-open, Arc<Mutex> per graph
    ├── protocol.rs   # Request/Response/ClientMessage/ServerMessage types
    └── http.rs       # Axum HTTP server + embedded GUI (feature = "gui")

Cargo features

Feature	Included in default	Description
repl	yes	Interactive REPL (rustyline, readline history)
server	yes	TCP server (tokio, SHA-256 auth)
gui	yes	Embedded HTTP GUI (axum); requires server
python	no	PyO3 Python bindings; build with maturin develop --features python

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License

minigdb is distributed under the GNU Lesser General Public License v3.0.