satwikmishra11 opened a new issue, #22131:
URL: https://github.com/apache/datafusion/issues/22131
### Is your feature request related to a problem or challenge?
## Summary
Following the SQL Diagnostics framework introduced in v46.0.0, I'd like to
extend
it to cover function argument type errors — one of the most common and
confusing
error categories for end users.
## Motivation
The 46.0.0 release blog explicitly noted:
> "Currently, diagnostics cover unresolved table/column references, missing
GROUP BY
> columns, ambiguous references, wrong number of UNION columns, type
mismatches, and
> a few others. **Future releases will extend this to more error types.**"
Right now, calling a function with a wrong argument type produces a generic
error
with no source location:
```sql
SELECT sqrt('hello');
```
### Describe the solution you'd like
The user gets no span, no pointer to which argument is wrong, and no hint
about
what type was expected. Compare this to how a missing GROUP BY column now
renders
with a precise highlight in the query text — the UX gap is significant.
## Proposed Change
Extend the existing `Diagnostic` / `DiagnosticEntry` framework
(`datafusion/common/src/diagnostic.rs`) so that when the
planner/type-coercion
layer rejects a scalar function call due to argument type mismatch, the
emitted
error includes:
1. A `Diagnostic` that attaches a **source span** pointing to the offending
argument expression in the original SQL query text.
2. A human-readable note of the form:
`"function 'sqrt' does not support argument of type Utf8 at position 1;
expected a numeric type"`
This matches the style and severity conventions already used in the existing
diagnostic emission sites.
## Scope
Minimum viable coverage (to keep the PR reviewable):
- [ ] Math functions called with a non-numeric argument
e.g. `SELECT sqrt('hello')`, `SELECT abs(true)`
- [ ] String functions called with a non-string argument
e.g. `SELECT length(3.14)` (where implicit coercion does not apply)
- [ ] Sqllogictest `.slt` test cases verifying the diagnostic text is
present
in the error output for each covered case
- [ ] No regression in existing tests
Out of scope for this PR (can be follow-ups):
- Aggregate or window function argument errors
- Errors arising from the wrong *number* of arguments (separate error path)
## Files I Plan to Touch
| File | Reason |
|------|--------|
| `datafusion/sql/src/planner/expr.rs` | Where SQL AST exprs are resolved;
span info is available here |
| `datafusion/expr/src/type_coercion/functions.rs` | Where argument type
checking fires |
| `datafusion/common/src/diagnostic.rs` | `Diagnostic` / `DiagnosticEntry`
types — read-only reference |
| `datafusion/sqllogictest/test_files/` | New `.slt` test cases |
## Questions Before I Start
1. **Is this the right layer to attach spans?** My reading is that `expr.rs`
in
the planner is the right place (since the AST span is still available
there),
rather than deeper in `type_coercion/`. Happy to be corrected.
2. **Is @eliaperantoni or another committer willing to be the supervising
maintainer for this?** Per the contributor guide, I want to confirm
there's
someone interested in reviewing before investing significant time. I
don't want
to submit a PR that sits unreviewed.
3. **Any prior art or in-flight PRs I should be aware of?** I searched open
issues
and PRs and didn't find an active effort here, but I may have missed
something.
## References
- [DataFusion 46.0.0 release blog — SQL Diagnostics
section](https://datafusion.apache.org/blog/2025/03/24/datafusion-46.0.0/)
-
[`datafusion/common/src/diagnostic.rs`](https://github.com/apache/datafusion/blob/main/datafusion/common/src/diagnostic.rs)
- Contributor guide: [Discussing New
Features](https://datafusion.apache.org/contributor-guide/roadmap.html)
Happy to iterate on scope or approach based on feedback here before writing
any code.
### Describe alternatives you've considered
_No response_
### Additional context
_No response_
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
