Stabilising changes for version 3.0.0

[amunra]

Overview

This PR is about tying up loose ends for a stable v. 3.0.0 of the client.
If we get feedback, we should add any extra fixup to the list below.

Task list

• @javier: Updated front page doc and examples that are consistent across all clients.
• JSON-driven array tests
• When writing an array, check if the data buffer can be written as-is.
  • If PyArray_ISCARRAY_RO returns true, it should call just call
    line_sender_buffer_column_f64_arr_row_major.
  • This should be a simpler and faster path that determining if the strides
    are default strides or not.
• Investigate what is earliest version of NumPy that our code supports.
  I've tested back to Numpy 1.26, but older versions may work as well.
  Once found, update pyproject.toml, then:
• Add a CI test run that just the Buffer Python tests, across different
  versions of NumPy.
  • To run the specific tests, run:
    export TEST_QUESTDB_PATCH_PATH=1
    python3 test/test.py -v TestBufferProtocolVersionV2
  • To quickly run Python with specific dependencies in a virtual environment,
    use uv: https://docs.astral.sh/uv/getting-started/installation/
    Then run uv run --with 'numpy==1.26.0' test/test.py -v TestBufferProtocolVersionV2
    See: https://docs.astral.sh/uv/guides/scripts/#running-a-script-with-dependencies
  • Context: The uv tool installs Python packages much faster than Python's
    default pip tool. It's a really cool tool, worth learning about.
  • I would suggest a completely separate CI step that only executes on Linux.
    There's no point doing this cross-platforms.
  • Ideally without a for loop, instead just flat steps in CI, one per numpy
    version.
  • We obviously don't need to test every single version. Take 5 or so "sample"
    versions. This is just to ensure that we don't regress the code in the future.
• Fix Sphinx API docs
  • Fix datetime.datetime in Python Sphinx API docs
  • Run ./proj clean && ./proj build && ./proj doc to regenerate the docs
  • Clean-building the docs will issue more warnings, these need to be fixed.
  • The issue is that the docs reference datetime which is only imported in
    Cython and not in Python, so the type can't be found.
  • Same for cross-linking to numpy.ndarray in the docs.
  • Tip: Run ./proj doc 1 to launch docs in the web browser.
• Fix a SyntaxWarning in the tests:

  test_dataframe.py:1572: SyntaxWarning: invalid escape sequence '\['
  "Unsupported dtype int16\[pyarrow\] for column 'a'.*github"):
  

• Update and document (front page + examples + api docs) which is the first
  version of QuestDB supports arrays.
  My guess is that it is going to be 8.4.0, but we need to confirm this.
  (I've also added this todo to the Rust/C/C++ client TODO list.)
• Once the next QuestDB release is cut, we should ensure that the CI tests
  pick up the latest version of QuestDB and run protocol version 2 tests against
  the server. We should also retain a CI test run that runs
  against an older version of QuestDB (e.g. 8.3.3) to ensure that we don't
  introduce regressions against protocol version 1.
• Update CHANGELOG date before releasing.
• Update stable+pre-release sections of README.rst.

Tandem PR

Related c-questdb-client PR: questdb/c-questdb-client#105