djanand opened a new pull request, #1883:
URL: https://github.com/apache/datafusion-ballista/pull/1883
# Which issue does this PR close?
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Closes #.
# Rationale for this change
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The `%%sql` Jupyter cell magic advertises two options in its help text that
were never actually implemented:
--no-display - Don't display results
--limit N - Limit displayed rows (default: 50)
The argument-parsing loop only extracted a variable name, it scanned *all*
tokens and kept the *last* non-flag, never breaking, silently dropping any
`--flag`. So the documented options were ignored. This PR makes the behavior
match
the documented contract, including the `(default: 50)` already promised in
the [help
text](https://github.com/apache/datafusion-ballista/blob/main/python/python/ballista/jupyter.py#L490-L491).
# What changes are included in this PR?
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In `python/python/ballista/jupyter.py`:
- Added `_parse_cell_magic_args()`, which parses `--limit N` and
`--no-display` plus the optional variable name, using the same hand-rolled
`line.split()` convention as the other magics in this module (`%ballista`,
`%register`). Invalid `--limit` values (missing / non-integer / non-positive)
return a clear message instead of raising.
- `--limit N` caps the **display** to N rows via datafusion's
`configure_formatter(max_rows=N, min_rows=N)`. This is display-only — it never
truncates the underlying data, so an in-query `LIMIT` always takes effect. When
`--limit` is omitted, the display falls back to a default of 50.
- `--no-display` runs the query, stores the result in the variable if one
is given, and renders nothing.
- Updated the `sql()` docstring and the `%ballista help` text.
Docs: added a short `--limit` / `--no-display` example to the "SQL Magic
Commands" section of `python/README.md`.
Tests in `python/python/tests/test_jupyter.py`:
- A cluster-free unit test for the argument parser (valid cases + invalid
`--limit` rejection).
- An integration test covering `--limit` (display cap set, data not
truncated), the default cap, `--no-display`, and the invalid-`--limit` error
path.
# Are there any user-facing changes?
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Yes, the previously documented `--limit` and `--no-display` options on the
`%%sql` cell magic now work. The README is updated accordingly.
The only behavioral change to existing usage: a `%%sql` cell now renders up
to **50** rows by default (the value the help text already documented
[here](https://github.com/apache/datafusion-ballista/blob/main/python/python/ballista/jupyter.py#L490-L491))
instead of datafusion's built-in default of 10. This affects rendered rows
only. Query results are never truncated, and in-query `LIMIT` is unaffected.
Note: `--limit` is implemented via datafusion's global HTML formatter, so
each `%%sql` cell re-sets the display cap. The cap also applies to subsequent
non-`%%sql`
DataFrame displays in the same kernel until changed
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