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Improve error messages when coercion fails #19004

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Improve error messages when coercion fails#19004
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saadtajwar
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enhancementNew feature or request

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@alamb
alamb
opened on Nov 30, 2025

Is your feature request related to a problem or challenge?

After #18820 is merged, running this query:

select array_slice(arrow_cast(make_array(1, 2, 3, 4, 5), 'ListView(Int64)'), 0, 6),
       array_slice(arrow_cast(make_array('h', 'e', 'l', 'l', 'o'), 'ListView(Utf8)'), 0, 5);

Results in a very hard to interpret error message:

DataFusion error: Error during planning: Failed to coerce arguments to satisfy a call to 'array_slice' function: coercion from ListView(Int64), Int64, Int64 to the signature OneOf([ArraySignature(Array { arguments: [Array, Index, Index], array_coercion: Some(FixedSizedListToList) }), ArraySignature(Array { arguments: [Array, Index, Index, Index], array_coercion: Some(FixedSizedListToList) })]) failed No function matches the given name and argument types 'array_slice(ListView(Int64), Int64, Int64)'. You might need to add explicit type casts.

As a user I would be pretty hard pressed to understand the actual problem is that array_slice doesn't support the ListView type

Describe the solution you'd like

I would like the error message to be more human readable

Describe alternatives you've considered

The error message for array_reverse seems much easier to understand:

> select array_reverse(arrow_cast(make_array(1, 2, 3, 4, 5), 'ListView(Int64)'));

Error during planning: array_reverse does not support type ListView(Int64) No function matches the given name and argument types 'array_reverse(ListView(Int64))'. You might need to add explicit type casts.
	Candidate functions:
	array_reverse(array)```

Perhaps something like

DataFusion error: Error during planning: Failed to coerce arguments to satisfy a call to 'array_slice' function. You might need to add explicit type casts.
	Candidate functions:
        array_slice(array, index, index)
        array_slice(array index, index, index)

I am not really sure how to work in the information that "Array" in this context means ListArray, LargeListArray or FixedSizeListArray

Additional context

No response

Activity

  1. alamb
    added the
    Feature
    issue type on Nov 30, 2025
  2. alamb
    added
    enhancementNew feature or request
    on Nov 30, 2025

  3. Jefffrey commented on Nov 30, 2025

    @Jefffrey
    Jefffrey
    on Nov 30, 2025
    Contributor

    Thanks for creating this, been meaning to do so but lost track 😅

  4. jatinkumarsingh commented on Dec 1, 2025

    @jatinkumarsingh
    jatinkumarsingh
    on Dec 1, 2025
    Contributor

    @alamb
    sir i would love to work on this issue too
    could u plz assign it to me

  5. jatinkumarsingh commented on Dec 1, 2025

    @jatinkumarsingh
    jatinkumarsingh
    on Dec 1, 2025
    Contributor

    take

  6. github-actions
    assigned
    jatinkumarsingh
    on Dec 1, 2025

  7. Jefffrey commented on Dec 10, 2025

    @Jefffrey
    Jefffrey
    on Dec 10, 2025
    Contributor

    I'll add on to this issue, we should look into improving the error message when using coercion API too. For example:

    > select log('');
Error during planning: Internal error: Function 'log' failed to match any signature, errors: Internal error: Expect TypeSignatureClass::Decimal but received NativeType::String, DataType: Utf8.
This issue was likely caused by a bug in DataFusion's code. Please help us to resolve this by filing a bug report in our issue tracker: https://github.com/apache/datafusion/issues,Internal error: Expect TypeSignatureClass::Float but received NativeType::String, DataType: Utf8.
This issue was likely caused by a bug in DataFusion's code. Please help us to resolve this by filing a bug report in our issue tracker: https://github.com/apache/datafusion/issues,Error during planning: Function 'log' expects 2 arguments but received 1,Error during planning: Function 'log' expects 2 arguments but received 1.
This issue was likely caused by a bug in DataFusion's code. Please help us to resolve this by filing a bug report in our issue tracker: https://github.com/apache/datafusion/issues No function matches the given name and argument types 'log(Utf8)'. You might need to add explicit type casts.
        Candidate functions:
        log(Coercion(TypeSignatureClass::Decimal))
        log(Coercion(TypeSignatureClass::Float, implicit_coercion=ImplicitCoercion([Numeric], default_type=Float64))
        log(Coercion(TypeSignatureClass::Float, implicit_coercion=ImplicitCoercion([Numeric], default_type=Float64), Coercion(TypeSignatureClass::Decimal))
        log(Coercion(TypeSignatureClass::Float, implicit_coercion=ImplicitCoercion([Numeric], default_type=Float64), Coercion(TypeSignatureClass::Float, implicit_coercion=ImplicitCoercion([Numeric], default_type=Float64))

    It's not very readable, and it includes InternalError which is not right in terms of semantics.

    This can be tackled as a separate task, with this issue as a wider tracking issue.

  8. Jefffrey commented on Dec 25, 2025

    @Jefffrey
    Jefffrey
    on Dec 25, 2025
    Contributor

    Hey @jatinkumarsingh , how's the progress going on this?

  9. Jefffrey
    assigned
    Jefffrey
    and unassigned
    jatinkumarsingh
    on Dec 27, 2025

  10. Jefffrey commented on Dec 27, 2025

    @Jefffrey
    Jefffrey
    on Dec 27, 2025
    Contributor

    I'll take over this as I think it's important to finally tackle this as part of other efforts to use the coercible API

  11. github-merge-queue
    added a commit that references this issue on Jan 1, 2026

    Refactor duplicate code in `type_coercion/functions.rs` (#19518)

    0db668b
  12. github-merge-queue
    added 2 commits that reference this issue on Jan 22, 2026

    Improve error message when string functions receive Binary types (#19819

    cf76352

    Further refactoring of type coercion function code (#19603)

    a77e5a5
  13. github-merge-queue
    added a commit that references this issue on Mar 4, 2026

    Improve formatting of datatypes (#20605)

    3b028fe
  14. de-bgunter
    added 3 commits that reference this issue on Mar 24, 2026

    Improve error message when string functions receive Binary types (apa…

    47b9d42

    Further refactoring of type coercion function code (apache#19603)

    5c233de

    Improve formatting of datatypes (apache#20605)

    557b9f3
  15. Jefffrey
    removed their assignment
    on Apr 16, 2026

  16. saadtajwar commented on Jun 30, 2026

    @saadtajwar
    saadtajwar
    on Jun 30, 2026
    Contributor

    Hey @alamb / @Jefffrey - is this one still open? Happy to work on this if so :)

  17. alamb commented on Jul 1, 2026

    @alamb
    alamb
    on Jul 1, 2026
    ContributorAuthor

    Hey @alamb / @Jefffrey - is this one still open? Happy to work on this if so :)

    Yes thank you -- perhaps you can start with some research into the current behavior and then we can figure out how what the curent status and what it should look like after that

  18. saadtajwar commented on Jul 1, 2026

    @saadtajwar
    saadtajwar
    on Jul 1, 2026
    Contributor

    @alamb - sounds good, thank you! I'll start with some digging now and report back with my findings! 😁

  19. saadtajwar commented on Jul 1, 2026

    @saadtajwar
    saadtajwar
    on Jul 1, 2026
    Contributor

    take

  20. github-actions
    assigned
    saadtajwar
    on Jul 1, 2026
  21. akoshchiy
    added a commit that references this issue on Oct 16, 2026

    fix: report OneOf signature mismatches as planning errors (apache#26329)

    81824e8
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