This is a Python library that binds to Apache Arrow in-memory query engine DataFusion.
Like pyspark, it allows you to build a plan through SQL or a DataFrame API against in-memory data, parquet or CSV files, run it in a multi-threaded environment, and obtain the result back in Python.
The major advantage of this library over other execution engines is that this library achieves zero-copy between Python and its execution engine: there is no cost in using UDFs, UDAFs, and collecting the results to Python apart from having to lock the GIL when running those operations.
Its query engine, DataFusion, is written in Rust, which makes strong assumptions about thread safety and lack of memory leaks.
Technically, zero-copy is achieved via the c data interface.
Simple usage:
import ballista
ctx = ballista.BallistaContext(host="host.docker.internal")
ctx.register_parquet("table", "/data")
df = ctx.sql("SELECT * FROM table LIMIT 10")
df.show()pip install ballista
# or
python -m pip install ballistaYou can verify the installation by running:
>>> import ballista
>>> ballista.__version__
'0.6.0'This assumes that you have rust and cargo installed. We use the workflow recommended by pyo3 and maturin.
Bootstrap:
# fetch this repo
git clone git@github.com:datafusion-contrib/datafusion-python.git
# prepare development environment (used to build wheel / install in development)
python3 -m venv venv
# activate the venv
source venv/bin/activate
# update pip itself if necessary
python -m pip install -U pip
# install dependencies (for Python 3.8+)
python -m pip install -r requirements-310.txtWhenever rust code changes (your changes or via git pull):
# make sure you activate the venv using "source venv/bin/activate" first
maturin develop
python -m pytestTo change test dependencies, change the requirements.in and run
# install pip-tools (this can be done only once), also consider running in venv
python -m pip install pip-tools
python -m piptools compile --generate-hashes -o requirements-310.txtTo update dependencies, run with -U
python -m piptools compile -U --generate-hashes -o requirements-310.txtMore details here