simd-r-drive-py 0.4.1a5

SIMD-optimized append-only schema-less storage engine. Key-based binary storage in a single-file storage container.

SIMD R Drive (Python Bindings)

Experimental Python bindings for SIMD R Drive — a high-performance, schema-less storage engine using a single-file storage container optimized for zero-copy binary access, written in Rust.

This library provides access to core functionality of simd-r-drive from Python, including high-performance key/value storage, zero-copy reads via memoryview, and support for streaming writes and reads.

⚠ Threaded streaming writes from Python are not supported. See Thread Safety for important limitations.

Features

• 🔑 Append-only key/value storage
• ⚡ Zero-copy reads via memoryview and mmap
• 📆 Single-file binary container (no schema or serialization required)
• ↺ Streaming interface for writing and reading large entries
• 🐍 Native Rust extension module for Python (via PyO3)

Supported Environments

The simd_r_drive_py Python bindings are built as native extension modules and require environments that support both Python and Rust toolchains.

✅ Platforms

• Linux (x86_64, aarch64)
• macOS (x86_64, arm64/M1/M2)

Wheels are built using cibuildwheel and tested on GitHub Actions.

✅ Supported Python Versions

• Python 3.10 – 3.13

Older versions (≤3.9) are explicitly skipped during wheel builds.

❌ Not Supported

• Windows (x86_64, AMD64, ARM64) Python bindings are not officially supported on Windows due to platform-specific filesystem and memory-mapping inconsistencies in the Python runtime.

  The underlying Rust library works on Windows and is tested continuously, but the Python bindings fail some unit tests in CI. Manual builds (including AMD64 and ARM64) have succeeded locally but are not considered production-stable.

• Python < 3.10
• 32-bit Python
• musl-based Linux environments (e.g., Alpine Linux)
• PyPy or other alternative Python interpreters

If you need support for other environments or interpreters, consider compiling from source with maturin develop inside a compatible environment.

Storage Layout

Offset Range	Field	Size (Bytes)	Description
0 → N	Payload	N	Variable-length data
N → N + 8	Key Hash	8	64-bit XXH3 hash of the key (fast lookups)
N + 8 → N + 16	Prev Offset	8	Absolute offset pointing to the previous version
N + 16 → N + 20	Checksum	4	32-bit CRC32C checksum for integrity verification

Installation

pip install -i simd-r-drive-py

Usage

Regular Writes and Reads

from simd_r_drive import DataStore

# Create or open a datastore
store = DataStore("mydata.bin")

# Write a key/value pair
store.write(b"username", b"jdoe")

# Read the value
value = store.read(b"username")
print(value)  # b'jdoe'

# Check existence
assert store.exists(b"username")

# Delete the key
store.delete(b"username")
assert store.read(b"username") is None

Batch Writes

from simd_r_drive import DataStore

store = DataStore("batch.bin")

# Prepare entries as a list of (key, value) byte tuples
entries = [
    (b"user:1", b"alice"),
    (b"user:2", b"bob"),
    (b"user:3", b"charlie"),
]

# Write all entries in a single batch
store.batch_write(entries)

# Verify that all entries were written correctly
for key, value in entries:
    assert store.read(key) == value

Streamed Writes and Reads (Large Payloads)

from simd_r_drive import DataStore
import io

store = DataStore("streamed.bin")

# Simulated payload — in practice, this could be any file-like stream,
# including one that does not fit entirely into memory.
payload = b"x" * (10 * 1024 * 1024)  # Example: 10 MB of dummy data
stream = io.BytesIO(payload)

store.write_stream(b"large-file", stream)

# Read the payload back in chunks
read_stream = store.read_stream(b"large-file")
result = bytearray()

for chunk in read_stream:
    result.extend(chunk)

assert result == payload

API

DataStore(path: str)

Opens (or creates) a file-backed storage container at the given path.

.write(key: bytes, value: bytes) -> None

Atomically appends a new key-value entry. Overwrites any previous version of the key.

.batch_write(items: List[Tuple[bytes, bytes]]) -> None

Writes multiple key-value pairs in a single operation. Each item must be a tuple of (key, value) where both are bytes.

.write_stream(key: bytes, reader: IO[bytes]) -> None

Streams from a Python file-like object (.read(n) interface). Not thread-safe.

.read(key: bytes) -> Optional[bytes]

Returns the full value for a key, or None if the key does not exist.

.read_entry(key: bytes) -> Optional[EntryHandle]

Returns a memory-mapped handle, exposing .as_memoryview() for zero-copy access.

.read_stream(key: bytes) -> Optional[EntryStream]

Returns a streaming reader exposing .read(n).

.delete(key: bytes) -> None

Marks an entry as deleted and no longer available to be read. The file remains append-only; use Rust-side compaction if needed.

.exists(key: bytes) -> bool

Returns whether a key is currently valid in the index.

Thread Safety

This Python binding is not thread-safe.

Due to Python’s Global Interpreter Lock (GIL) and the limitations of PyO3, concurrent streaming writes or reads from multiple threads are not supported, and doing so may cause hangs or inconsistent behavior.

• ⚠ Use only from a single thread.
• ❌ Do not call methods like write_stream or read_stream from multiple threads.
• ❌ Do not share a DataStore instance across threads.
• ✅ For concurrent, high-performance use — especially with streaming — use the native Rust version directly.

This design avoids working around the GIL or spawning internal locks for artificial concurrency. If you need reliable multithreading, call into the Rust API instead.

Limitations

• Python bindings currently lack async support.
• write_stream is blocking and not safe for concurrent use.
• Compaction is not yet exposed via Python.
• This is not a drop-in database — you're expected to manage your own data formats.

Development

To develop and test the Python bindings:

Requirements

• Python 3.10 or above
• Rust toolchain (with cargo)

pip install -r requirements.txt -r requirements-dev.txt

Test Changes

maturin develop # Builds the Rust library
pytest # Tests the Python integration

Build a Release Wheel

maturin build --release
pip install dist/simd_r_drive_py-*.whl

License

Licensed under the Apache-2.0 License.