Exclude zstandard from Python >= 3.14

[clemlesne]

Since Python 3.14, zstd is bundled as a standard Python lib; no need anymore for the zstandard dependency (see https://peps.python.org/pep-0784/ and facebook/zstd#4496).

Using clickhouse-connect with Python 3.14 requires a manual build of zstandard because it is not built anymore for this Python version. Builds are long and complex to set up.

Nevertheless, it requires a slightly different integration since its a native package; see compression.zstd.

Related:

• make zstandard optional #535

[joe-clickhouse]

Great catch! Thanks @clemlesne. I've started the work in getting 3.14 build support in #575. Thankfully, it looks like the API is the same for our use case here, but I'll need some conditional imports in the files where we use it I'll need to make an adjustment to the setup.py as well. Thanks again!

[joe-clickhouse]

Just to follow up here. I tried running the tests as is with the zstd that's now included with the 3.14 standard lib and it caused quite a few to fail. The API appears to be different enough to cause some problems with the way we're currently using it. Because of that, I'm still going to just rely on the third-party zstandard for now. As of zstandard>=0.24.0 python3.14 compatible wheels are provided so manual builds should not be required anymore. Nevertheless, I'll leave this issue open and we can decide later if supporting both would still be worth the effort. Thanks again!