Qenlo Python SDK

Type-safe Python bindings for Qenlo — the embedded, durable vector database written in Rust.

Qenlo provides exact filtered cosine vector search with atomic commits, write-ahead logging (WAL), and portable .qn snapshot files. Every search returns an execution report with routing and resource measurements.

Installation

pip install qenlo

Pre-built binary wheels bundle the native Rust engine for:

• Linux (x86_64, aarch64)
• macOS (Apple Silicon arm64, Intel x86_64)
• Windows (x86_64)

For source checkouts or development builds, set QENLO_LIBRARY_PATH to point to your compiled qenlo_ffi.dll, libqenlo_ffi.so, or libqenlo_ffi.dylib.

Quickstart

In-Memory Collection

from qenlo import Collection, Filter, Record

# Create an in-memory collection with 3-dimensional vectors
with Collection.memory(dimension=3) as db:
    # Insert records
    db.add(Record(id=1, user_id=42, timestamp=100, vector=(1.0, 0.0, 0.0)))
    db.add(Record(id=2, user_id=42, timestamp=200, vector=(0.0, 1.0, 0.0)))
    db.add(Record(id=3, user_id=99, timestamp=150, vector=(0.7, 0.7, 0.0)))

    # Search with combined user and timestamp filters
    response = db.search(
        query=(1.0, 0.0, 0.0),
        filter=Filter(user_id=42, timestamp_lower=50, timestamp_upper=150),
        k=5,
    )

    for hit in response.results:
        print(f"ID: {hit.id}, Cosine Distance: {hit.distance:.4f}")

    # Inspect the execution report
    report = response.report
    print(f"Backend: {report.actual_backend}, Algorithm: {report.algorithm}")
    print(f"Total Duration: {report.total_duration_ns} ns")

Durable Storage & Restarts

Qenlo collections can be persisted to disk with crash-safe write-ahead logging (WAL) and atomic compaction:

from qenlo import Collection, Record, Filter

path = "./my_collection.qenlo"

# 1. Create a new durable collection directory
with Collection.create(path, dimension=128) as db:
    db.add(Record(id=1, user_id=7, timestamp=10, vector=my_vector))
    db.flush()  # Compact and ensure full disk sync

# 2. Reopen across application restarts
with Collection.open(path, dimension=128) as db:
    response = db.search(query=my_query, filter=Filter(user_id=7), k=10)
    print(f"Found {len(response.results)} matches")

Portable .qn Interchange Files

Export and import standalone, checksummed, immutable .qn snapshots:

# Export an existing collection to a .qn file
db.export_qn("snapshots/v1.qn")

# Import from a .qn file into a fast in-memory collection
with Collection.import_qn("snapshots/v1.qn", dimension=128) as snapshot_db:
    stats = snapshot_db.stats()
    print(f"Loaded {stats.live_rows} rows from generation {stats.generation}")

Batch Operations

Qenlo supports high-throughput atomic batch mutations:

records = [
    Record(id=10, user_id=1, timestamp=1000, vector=(0.1, 0.2, 0.3)),
    Record(id=11, user_id=1, timestamp=1001, vector=(0.4, 0.5, 0.6)),
    Record(id=12, user_id=2, timestamp=1002, vector=(0.7, 0.8, 0.9)),
]

# Insert all atomically (all-or-nothing validation)
db.add_batch(records)

# Delete multiple records by ID
db.delete_batch([10, 11])

For an existing C-contiguous native float32 matrix, add_buffer avoids per-component Python assignment. Writable buffers are borrowed for the native call; read-only buffers incur one bulk copy. The Rust core copies and validates the complete batch before return.

Optional PyTorch index

Install the optional dependency only in desktop applications that already need PyTorch:

pip install 'qenlo[torch]'

TorchIndex is an exhaustive, resident FP32 matrix index. It is derived from a canonical collection and is not a second durable store:

from qenlo import Filter, TorchIndex

index = TorchIndex.from_collection(
    db,
    Filter(user_id=42),
    device="cuda",       # "cpu" and "mps" are also explicit choices
    max_bytes=256 << 20,
)
ids, distances = index.search(query_tensor, k=10)

The capture includes only live rows matching the filter and records the canonical generation. A later add or delete makes the index stale; search then raises instead of serving the old snapshot. Inputs are copied, normalized, and owned by the index. Returned IDs and distances are tensors on the selected device. The reported allocation_bytes and max_bytes checks cover owned vectors, IDs, and the explicit search tensors; they do not measure PyTorch allocator caches or backend-private memory.

Current tensor IDs are restricted to 0..=2**63-1. Native collections accept the full unsigned 64-bit range, but PyTorch documents uint64 eager operations as having limited backend support. TorchIndex.from_collection rejects a snapshot outside the portable tensor range without truncating it. CPU is tested locally; CUDA and MPS require separate platform runs.

Data Model & Types

Record

• id: int (unsigned 64-bit integer, unique and non-reusable)
• user_id: int (unsigned 64-bit integer)
• timestamp: int (signed 64-bit integer)
• vector: Sequence[float] (normalized FP32 components)

Filter

• user_id: Optional[int] (exact equality match)
• timestamp_lower: Optional[int] (inclusive lower bound)
• timestamp_upper: Optional[int] (exclusive upper bound)

ExecutionReport

• operation_id: int — Unique monotonically increasing query ID
• requested_backend: str — Cpu, GpuPredicate, or Automatic
• actual_backend: str — Hardware engine that executed the search
• algorithm: str — Search algorithm (Exact, IvfFlat, etc.)
• filter_execution: str — Filter strategy evaluated
• index_generation: int — Generation watermark observed
• total_duration_ns: int — Total wall-clock time in nanoseconds
• lock_wait_ns: int — Time spent acquiring read locks
• eligible_rows: Optional[int] — Number of live rows passing metadata filters
• upload_bytes: Optional[int] — Host-to-device bytes transferred
• readback_bytes: Optional[int] — Device-to-host bytes read back

Error Handling

All native and validation failures raise QenloError or standard Python exceptions (ValueError):

from qenlo import Collection, QenloError, Record

try:
    with Collection.memory(3) as db:
        db.add(Record(1, 1, 0, (1.0, 0.0, 0.0)))
        # Duplicate IDs are strictly rejected
        db.add(Record(1, 1, 0, (0.0, 1.0, 0.0)))
except QenloError as e:
    print(f"Operation rejected: {e}")

Background work and networking

Importing or using the Python SDK starts no background thread and sends no network request. Applications may export ExecutionReport values through their own telemetry system.

License

Dual-licensed under MIT or Apache-2.0 at your option.