[Python] Create tools to enable optional components (like Gandiva, Flight) to be built and deployed as separate Python packages

[asfimport]

Our current monolithic approach to Python packaging isn't likely to be sustainable long-term.

At a high level, I would propose a structure like this:

pip install pyarrow  # core package containing libarrow, libarrow_python, and any other common bundled C++ library dependencies

pip install pyarrow-flight  # installs pyarrow, pyarrow_flight

pip install pyarrow-gandiva # installs pyarrow, pyarrow_gandiva

We can maintain the semantic appearance of a single pyarrow package by having thin API modules that would look like

CONTENTS OF pyarrow/flight.py

from pyarrow_flight import *

Obviously, this is more difficult to build and package:

• CMake and setup.py files must be refactored a bit so that we can reuse code between the parent and child packages

• Separate conda and wheel packages must be produced. With conda this seems more straightforward but since the child wheels depend on the parent core wheel, the build process seems more complicated

  In any case, I don't think these challenges are insurmountable. This will have several benefits:

• Smaller installation footprint for simple use cases (though note we are STILL duplicating shared libraries in the wheels, which is quite bad)

• Less developer anxiety about expanding the scope of what Python code is shipped from apache/arrow. If in 5 years we are shipping 5 different Python wheels with each Apache Arrow release, that sounds completely fine to me.

Reporter: Wes McKinney / @wesm

PRs and other links:

• GitHub Pull Request #8390

_{Note: This issue was originally created as ARROW-8518. Please see the migration documentation for further details.}

[amol-]

https://github.com/amol-/consolidatewheels which was created for the purpose of splitting wheels in arrow. Requires real world testing on more complex cases than what https://github.com/amol-/wheeldeps can verify