timsaucer opened a new issue, #1727:
URL: https://github.com/apache/datafusion-python/issues/1727
Neither `datafusion-ffi-example` nor `datafusion-ffi-query-planner-example`
has a script you can run. They are 51 and 47 pytest assertions respectively.
Meanwhile `user-guide/data-sources.md:219` calls the first one a **"user
example"** and sends Python users there from the user guide, and
`io/table_provider.md:30` calls it "a complete example". We promise a runnable
example and deliver a test suite.
**Precedent:** `examples/tpch/` — the script is the artifact and a pytest
keeps it honest. CI already runs `pytest python/tests/_test*.py` in each crate
directory (`test.yml:136-150`), so a driver test needs **zero workflow
changes**.
Layout per crate: `run_demo.py` at the tree root, parallel to the existing
`examples/distributed/run_tpch.py`, and a driver at
`python/tests/_test_run_demo.py` that runs it via
`subprocess.run([sys.executable, script])` and asserts on anchor lines.
Subprocess rather than `import_module` or `runpy`, because it proves the thing
being asked for: that it runs standalone with no pytest around it.
Each script should open with an import guard that turns the one real failure
mode into an instruction rather than a traceback:
```python
try:
from datafusion_ffi_example import MyTableProvider
except ImportError:
sys.exit("build the extension first:\n uv run maturin develop\nSee
README.md.")
```
- [ ] **`datafusion-ffi-example/run_demo.py`** — walk the conformance matrix
in numbered sections: table provider, functions, catalog provider, config
extension, codec round-trip, then *the same bytes decoded a second time*. That
last section is only truthful after the logical-codec sub-issue lands, and it
is the one place in the repository where the guide's central rule is
demonstrated rather than asserted.
- [ ] **`datafusion-ffi-query-planner-example/run_demo.py`** — print plans,
not rows. Planner nesting is understood by seeing the indented tree, and the
existing tests assert on plan strings they never show. Cover the logical plan
handed to the planner, the physical plan returned, the effect of `SET
ffi_query_planner.max_rows`, and two planners nesting. Use `.display_indent()`.
- [ ] **`Role:` header on each tree's README**, so the label survives the
click from `examples/README.md`, which already distinguishes the trees but
loses the distinction as soon as you follow the link. Three lines: what this
tree is, where to go if you are learning the protocol, and how to run it.
**Scope note:** make them runnable, but do not promise
`datafusion-ffi-example` reads as a tutorial. It is a coverage matrix —
`.ai/skills/check-upstream/SKILL.md:455` instructs adding every new FFI type to
it — so it grows under protocol pressure rather than narrative need. The
planner crate is single-topic and can carry the stronger claim.
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