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Type signature matching errors are overly verbose and show internal details #20501
Description
Description
After upgrading to DataFusion 52, error messages for function signature mismatches have become less concise and helpful. When a user tries to call an aggregate function with an unsupported type, they now see verbose internal errors instead of user-friendly messages.
This regression was introduced in PR #18769 ("Refactor avg & sum signatures away from user defined"), which was part of the broader effort in #12725 to avoid use of Signature::user_defined.
To Reproduce
CREATE TABLE test (bool_col BOOLEAN);
SELECT SUM(bool_col) FROM test;Before (DataFusion 51):
Error during planning: Execution error: Function 'sum' user-defined coercion failed with "Execution error: Sum not supported for Boolean" No function matches the given name and argument types 'sum(Boolean)'. You might need to add explicit type casts.
Candidate functions:
sum(UserDefined)
The key message "Sum not supported for Boolean" was clear and actionable.
After (DataFusion 52):
Error during planning: Internal error: Function 'sum' failed to match any signature, errors: Internal error: Expect TypeSignatureClass::Decimal but received NativeType::Boolean, DataType: Boolean.
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::Native(LogicalType(Native(UInt64), UInt64)) but received NativeType::Boolean, DataType: Boolean.
This issue was likely caused by a bug in DataFusion's code...
[repeats for each signature variant]
Candidate functions:
sum(Coercion(TypeSignatureClass::Decimal))
sum(Coercion(TypeSignatureClass::Native(LogicalType(Native(UInt64), UInt64)), implicit_coercion=...))
...
Problems With New Error
- Misleading: Says "Internal error" and asks users to file a bug report, but this is a user error (wrong argument type), not a DataFusion bug
- Verbose: Shows every failed signature match attempt with internal type system details (
TypeSignatureClass::Native(LogicalType(...))) - Lost context: The meaningful message "Sum not supported for Boolean" is no longer present
Activity
alamb commentedon Feb 23, 2026
I think this might be related to some changes @Jefffrey might remember 🤔
Jefffrey commentedon Mar 2, 2026
Yeah #20070 (and the linked issues inside it) is meant to work towards solving this (along with #20605 it seems)
myandpr commentedon Mar 18, 2026
Hi @Jefffrey @alamb I spent a bit of time looking at this.
The immediate problem seems to be that
TypeSignature::OneOfturns overload/coercion failures into anInternal error, which then becomes user-visible during planning.Would it make sense to return a normal planning error here instead, while keeping the existing candidate-signature diagnostics?
That would not fully restore the older
Sum not supported for Booleanwording, but it should address the misleading internal-error behavior and the exposed internal type details.Would it also make sense to look at this implementation? #21032
fix: report OneOf signature mismatches as planning errors (apache#26329)