Function spark_concat

datafusion/spark/src/function/string/concat.rs:104–158

Concatenates strings, returning NULL if any input is NULL This is a Spark-specific wrapper around DataFusion's concat that returns NULL if any argument is NULL (Spark behavior), whereas DataFusion's concat ignores NULLs.

(args: ScalarFunctionArgs)

/// This is a Spark-specific wrapper around DataFusion's concat that returns NULL
/// if any argument is NULL (Spark behavior), whereas DataFusion's concat ignores NULLs.
fn spark_concat(args: ScalarFunctionArgs) -> Result<ColumnarValue> {
    let ScalarFunctionArgs {
        args: arg_values,
        arg_fields,
        number_rows,
        return_field,
        config_options,
    } = args;

    // Handle zero-argument case: return empty string
    if arg_values.is_empty() {
        let return_type = return_field.data_type();
        return match return_type {
            DataType::Utf8View => Ok(ColumnarValue::Scalar(ScalarValue::Utf8View(Some(
                String::new(),
            )))),
            DataType::LargeUtf8 => Ok(ColumnarValue::Scalar(ScalarValue::LargeUtf8(
                Some(String::new()),
            ))),
            _ => Ok(ColumnarValue::Scalar(ScalarValue::Utf8(
                Some(String::new()),
            ))),
        };
    }

    // Step 1: Check for NULL mask in incoming args
    let null_mask = compute_null_mask(&arg_values);

    // If all scalars and any is NULL, return NULL immediately
    if matches!(null_mask, NullMaskResolution::ReturnNull) {
        let return_type = return_field.data_type();
        return match return_type {
            DataType::Utf8View => Ok(ColumnarValue::Scalar(ScalarValue::Utf8View(None))),
            DataType::LargeUtf8 => {
                Ok(ColumnarValue::Scalar(ScalarValue::LargeUtf8(None)))
            }
            _ => Ok(ColumnarValue::Scalar(ScalarValue::Utf8(None))),
        };
    }

    // Step 2: Delegate to DataFusion's concat
    let concat_func = ConcatFunc::new();
    let return_type = return_field.data_type().clone();
    let func_args = ScalarFunctionArgs {
        args: arg_values,
        arg_fields,
        number_rows,
        return_field,
        config_options,
    };
    let result = concat_func.invoke_with_args(func_args)?;

    // Step 3: Apply NULL mask to result
    apply_null_mask(result, null_mask, &return_type)
}

#[cfg(test)]
mod tests {