Add arrow_metadata(<expr>) UDF #19356

Activity

1. Jefffrey commented on Dec 17, 2025

   

   Jefffrey

   on Dec 17, 2025

   Contributor

   More actions

   Existing reference:

   datafusion/datafusion/sqllogictest/src/test_context.rs

   Lines 406 to 453 in 2b67ba8

   	/// UDF to extract metadata from a field for testing purposes
   	/// Usage: get_metadata(expr, 'key') -> returns the metadata value or NULL
   	#[derive(Debug, PartialEq, Eq, Hash)]
   	struct GetMetadataUdf {
   	signature: Signature,
   	}
   	impl GetMetadataUdf {
   	fn new() -> Self {
   	Self {
   	signature: Signature::any(2, Volatility::Immutable),
   	}
   	}
   	}
   	impl ScalarUDFImpl for GetMetadataUdf {
   	fn as_any(&self) -> &dyn Any {
   	self
   	}
   	fn name(&self) -> &str {
   	"get_metadata"
   	}
   	fn signature(&self) -> &Signature {
   	&self.signature
   	}
   	fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> {
   	Ok(DataType::Utf8)
   	}
   	fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
   	// Get the metadata key from the second argument (must be a string literal)
   	let key = match &args.args[1] {
   	ColumnarValue::Scalar(ScalarValue::Utf8(Some(k))) => k.clone(),
   	_ => {
   	return exec_err!("get_metadata second argument must be a string literal")
   	}
   	};
   	// Get metadata from the first argument's field
   	let metadata_value = args.arg_fields[0].metadata().get(&key).cloned();
   	// Return as a scalar (same value for all rows)
   	Ok(ColumnarValue::Scalar(ScalarValue::Utf8(metadata_value)))
   	}
   	}

   As part of this issue, we should remove the above UDF and use the new arrow_metadata() UDF directly in the tests
2. github-merge-queue

   added a commit that references this issue on Dec 23, 2025

   Add:arrow_metadata() UDF (#19435)

   ...

   This issue will close once commit d844f86 is merged into the 'main' branch.

   d844f86
3. comphead

   closed this as completedin #19435on Dec 23, 2025