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Make lower and upper emit Utf8View for Utf8View input #20616

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Make lower and upper emit Utf8View for Utf8View input #20616

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837f896
Make lower emit Utf8View for Utf8View input
kumarUjjawal Feb 28, 2026
d92a711
Make lower and upper emit Utf8View for Utf8View input
kumarUjjawal Mar 2, 2026
d553ac1
Handle dictionary Utf8View return type in case conversion
kumarUjjawal Mar 2, 2026
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27 changes: 21 additions & 6 deletions datafusion/functions/src/string/common.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,9 +20,10 @@
use std::sync::Arc;

use crate::strings::make_and_append_view;
use crate::utils::utf8_to_str_type;
use arrow::array::{
Array, ArrayRef, GenericStringArray, GenericStringBuilder, NullBufferBuilder,
OffsetSizeTrait, StringBuilder, StringViewArray, new_null_array,
OffsetSizeTrait, StringViewArray, StringViewBuilder, new_null_array,
};
use arrow::buffer::{Buffer, ScalarBuffer};
use arrow::datatypes::DataType;
Expand Down Expand Up @@ -331,6 +332,22 @@ fn string_trim<T: OffsetSizeTrait, Tr: Trimmer>(args: &[ArrayRef]) -> Result<Arr
}
}

pub(crate) fn case_conversion_return_type(
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@neilconway neilconway Mar 2, 2026

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This doesn't seem specific to case conversion; we probably need a more generic facility for finding the return return type for a function that takes a string. But we can handle that later.

arg_type: &DataType,
name: &str,
) -> Result<DataType> {
match arg_type {
DataType::Utf8View | DataType::BinaryView => Ok(DataType::Utf8View),
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@neilconway neilconway Mar 2, 2026

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I believe BinaryView will be rejected by the type signatures for these functions, so probably clearer if we don't handle it.

DataType::Dictionary(_, value_type)
if **value_type == DataType::Utf8View
|| **value_type == DataType::BinaryView =>
{
Ok(DataType::Utf8View)
}
_ => utf8_to_str_type(arg_type, name),
}
}

pub(crate) fn to_lower(args: &[ColumnarValue], name: &str) -> Result<ColumnarValue> {
case_conversion(args, |string| string.to_lowercase(), name)
}
Expand Down Expand Up @@ -358,10 +375,8 @@ where
>(array, op)?)),
DataType::Utf8View => {
let string_array = as_string_view_array(array)?;
let mut string_builder = StringBuilder::with_capacity(
string_array.len(),
string_array.get_array_memory_size(),
);
let mut string_builder =
StringViewBuilder::with_capacity(string_array.len());

for str in string_array.iter() {
if let Some(str) = str {
Expand All @@ -386,7 +401,7 @@ where
}
ScalarValue::Utf8View(a) => {
let result = a.as_ref().map(|x| op(x));
Ok(ColumnarValue::Scalar(ScalarValue::Utf8(result)))
Ok(ColumnarValue::Scalar(ScalarValue::Utf8View(result)))
}
other => exec_err!("Unsupported data type {other:?} for function {name}"),
},
Expand Down
37 changes: 31 additions & 6 deletions datafusion/functions/src/string/lower.rs
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Expand Up @@ -18,8 +18,7 @@
use arrow::datatypes::DataType;
use std::any::Any;

use crate::string::common::to_lower;
use crate::utils::utf8_to_str_type;
use crate::string::common::{case_conversion_return_type, to_lower};
use datafusion_common::Result;
use datafusion_common::types::logical_string;
use datafusion_expr::{
Expand Down Expand Up @@ -82,7 +81,7 @@ impl ScalarUDFImpl for LowerFunc {
}

fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
utf8_to_str_type(&arg_types[0], "lower")
case_conversion_return_type(&arg_types[0], "lower")
}

fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
Expand All @@ -97,8 +96,7 @@ impl ScalarUDFImpl for LowerFunc {
#[cfg(test)]
mod tests {
use super::*;
use arrow::array::{Array, ArrayRef, StringArray};
use arrow::datatypes::DataType::Utf8;
use arrow::array::{Array, ArrayRef, StringArray, StringViewArray};
use arrow::datatypes::Field;
use datafusion_common::config::ConfigOptions;
use std::sync::Arc;
Expand All @@ -111,7 +109,7 @@ mod tests {
number_rows: input.len(),
args: vec![ColumnarValue::Array(input)],
arg_fields,
return_field: Field::new("f", Utf8, true).into(),
return_field: Field::new("f", expected.data_type().clone(), true).into(),
config_options: Arc::new(ConfigOptions::default()),
};

Expand Down Expand Up @@ -197,4 +195,31 @@ mod tests {

to_lower(input, expected)
}

#[test]
fn lower_utf8view() -> Result<()> {
let input = Arc::new(StringViewArray::from(vec![
Some("ARROW"),
None,
Some("TSCHÜSS"),
])) as ArrayRef;

let expected = Arc::new(StringViewArray::from(vec![
Some("arrow"),
None,
Some("tschüss"),
])) as ArrayRef;

to_lower(input, expected)
}

#[test]
fn lower_return_type_dictionary_utf8view() -> Result<()> {
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@neilconway neilconway Mar 2, 2026

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For symmetry, should we add an analogous test case for upper?

let return_type = LowerFunc::new().return_type(&[DataType::Dictionary(
Box::new(DataType::Int32),
Box::new(DataType::Utf8View),
)])?;
assert_eq!(return_type, DataType::Utf8View);
Ok(())
}
}
27 changes: 21 additions & 6 deletions datafusion/functions/src/string/upper.rs
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Expand Up @@ -15,8 +15,7 @@
// specific language governing permissions and limitations
// under the License.

use crate::string::common::to_upper;
use crate::utils::utf8_to_str_type;
use crate::string::common::{case_conversion_return_type, to_upper};
use arrow::datatypes::DataType;
use datafusion_common::Result;
use datafusion_common::types::logical_string;
Expand Down Expand Up @@ -81,7 +80,7 @@ impl ScalarUDFImpl for UpperFunc {
}

fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
utf8_to_str_type(&arg_types[0], "upper")
case_conversion_return_type(&arg_types[0], "upper")
}

fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
Expand All @@ -96,8 +95,7 @@ impl ScalarUDFImpl for UpperFunc {
#[cfg(test)]
mod tests {
use super::*;
use arrow::array::{Array, ArrayRef, StringArray};
use arrow::datatypes::DataType::Utf8;
use arrow::array::{Array, ArrayRef, StringArray, StringViewArray};
use arrow::datatypes::Field;
use datafusion_common::config::ConfigOptions;
use std::sync::Arc;
Expand All @@ -110,7 +108,7 @@ mod tests {
number_rows: input.len(),
args: vec![ColumnarValue::Array(input)],
arg_fields: vec![arg_field],
return_field: Field::new("f", Utf8, true).into(),
return_field: Field::new("f", expected.data_type().clone(), true).into(),
config_options: Arc::new(ConfigOptions::default()),
};

Expand Down Expand Up @@ -196,4 +194,21 @@ mod tests {

to_upper(input, expected)
}

#[test]
fn upper_utf8view() -> Result<()> {
let input = Arc::new(StringViewArray::from(vec![
Some("arrow"),
None,
Some("tschüß"),
])) as ArrayRef;

let expected = Arc::new(StringViewArray::from(vec![
Some("ARROW"),
None,
Some("TSCHÜSS"),
])) as ArrayRef;

to_upper(input, expected)
}
}
30 changes: 30 additions & 0 deletions datafusion/sqllogictest/test_files/functions.slt
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Expand Up @@ -445,6 +445,21 @@ SELECT upper(arrow_cast('árvore ação αβγ', 'Dictionary(Int32, Utf8)'))
----
ÁRVORE AÇÃO ΑΒΓ

query T
SELECT arrow_typeof(upper('foo'))
----
Utf8

query T
SELECT arrow_typeof(upper(arrow_cast('foo', 'LargeUtf8')))
----
LargeUtf8

query T
SELECT arrow_typeof(upper(arrow_cast('foo', 'Utf8View')))
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@neilconway neilconway Mar 2, 2026

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Add SLT tests for dictionary with a Utf8View value type?

----
Utf8View

query T
SELECT btrim(' foo ')
----
Expand Down Expand Up @@ -500,6 +515,21 @@ SELECT lower(arrow_cast('ÁRVORE AÇÃO ΑΒΓ', 'Dictionary(Int32, Utf8)'))
----
árvore ação αβγ

query T
SELECT arrow_typeof(lower('FOObar'))
----
Utf8

query T
SELECT arrow_typeof(lower(arrow_cast('FOObar', 'LargeUtf8')))
----
LargeUtf8

query T
SELECT arrow_typeof(lower(arrow_cast('FOObar', 'Utf8View')))
----
Utf8View

query T
SELECT ltrim(' foo')
----
Expand Down