Make translate emit Utf8View for Utf8View input (#20624)

## Which issue does this PR close?

- Part of #20585

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## Rationale for this change

String UDFs should preserve string representation where feasible.
`translate` previously accepted Utf8View input but emitted Utf8, causing
an unnecessary type downgrade. This aligns `translate` with the expected
behavior of returning the same string type as its primary input.

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in the issue then this section is not needed.
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## What changes are included in this PR?

1. Updated `translate` return type inference to emit Utf8View when input
is Utf8View, while preserving existing behavior for Utf8 and LargeUtf8.
2. Refactored `translate` and `translate_with_map` to use explicit
string builders (via a local `TranslateOutput` helper trait) instead of
`.collect::<GenericStringArray<T>>()`, so the correct output array type
is produced for each input type.
3. Added unit tests for Utf8View input (basic, null, non-ASCII) and
sqllogictests verifying `arrow_typeof` output for all three string
types.

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## Are these changes tested?

Yes. Unit tests and sqllogictests are included.

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## Are there any user-facing changes?

No.

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Author: shivaaang

datafusion/functions/src/unicode/translate.rs

@@ -16,16 +16,16 @@
 // under the License.
 
 use std::any::Any;
-use std::sync::Arc;
 
 use arrow::array::{
-    ArrayAccessor, ArrayIter, ArrayRef, AsArray, GenericStringArray, OffsetSizeTrait,
+    ArrayAccessor, ArrayIter, ArrayRef, AsArray, LargeStringBuilder, StringBuilder,
+    StringLikeArrayBuilder, StringViewBuilder,
 };
 use arrow::datatypes::DataType;
 use datafusion_common::HashMap;
 use unicode_segmentation::UnicodeSegmentation;
 
-use crate::utils::{make_scalar_function, utf8_to_str_type};
+use crate::utils::make_scalar_function;
 use datafusion_common::{Result, exec_err};
 use datafusion_expr::TypeSignature::Exact;
 use datafusion_expr::{
@@ -93,7 +93,7 @@ impl ScalarUDFImpl for TranslateFunc {
     }
 
     fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
-        utf8_to_str_type(&arg_types[0], "translate")
+        Ok(arg_types[0].clone())
     }
 
     fn invoke_with_args(
@@ -116,33 +116,42 @@ impl ScalarUDFImpl for TranslateFunc {
             let ascii_table = build_ascii_translate_table(from_str, to_str);
 
             let string_array = args.args[0].to_array_of_size(args.number_rows)?;
+            let len = string_array.len();
 
             let result = match string_array.data_type() {
                 DataType::Utf8View => {
                     let arr = string_array.as_string_view();
-                    translate_with_map::<i32, _>(
+                    let builder = StringViewBuilder::with_capacity(len);
+                    translate_with_map(
                         arr,
                         &from_map,
                         &to_graphemes,
                         ascii_table.as_ref(),
+                        builder,
                     )
                 }
                 DataType::Utf8 => {
                     let arr = string_array.as_string::<i32>();
-                    translate_with_map::<i32, _>(
+                    let builder =
+                        StringBuilder::with_capacity(len, arr.value_data().len());
+                    translate_with_map(
                         arr,
                         &from_map,
                         &to_graphemes,
                         ascii_table.as_ref(),
+                        builder,
                     )
                 }
                 DataType::LargeUtf8 => {
                     let arr = string_array.as_string::<i64>();
-                    translate_with_map::<i64, _>(
+                    let builder =
+                        LargeStringBuilder::with_capacity(len, arr.value_data().len());
+                    translate_with_map(
                         arr,
                         &from_map,
                         &to_graphemes,
                         ascii_table.as_ref(),
+                        builder,
                     )
                 }
                 other => {
@@ -172,24 +181,30 @@ fn try_as_scalar_str(cv: &ColumnarValue) -> Option<&str> {
 }
 
 fn invoke_translate(args: &[ArrayRef]) -> Result<ArrayRef> {
+    let len = args[0].len();
     match args[0].data_type() {
         DataType::Utf8View => {
             let string_array = args[0].as_string_view();
             let from_array = args[1].as_string::<i32>();
             let to_array = args[2].as_string::<i32>();
-            translate::<i32, _, _>(string_array, from_array, to_array)
+            let builder = StringViewBuilder::with_capacity(len);
+            translate(string_array, from_array, to_array, builder)
         }
         DataType::Utf8 => {
             let string_array = args[0].as_string::<i32>();
             let from_array = args[1].as_string::<i32>();
             let to_array = args[2].as_string::<i32>();
-            translate::<i32, _, _>(string_array, from_array, to_array)
+            let builder =
+                StringBuilder::with_capacity(len, string_array.value_data().len());
+            translate(string_array, from_array, to_array, builder)
         }
         DataType::LargeUtf8 => {
             let string_array = args[0].as_string::<i64>();
             let from_array = args[1].as_string::<i32>();
             let to_array = args[2].as_string::<i32>();
-            translate::<i64, _, _>(string_array, from_array, to_array)
+            let builder =
+                LargeStringBuilder::with_capacity(len, string_array.value_data().len());
+            translate(string_array, from_array, to_array, builder)
         }
         other => {
             exec_err!("Unsupported data type {other:?} for function translate")
@@ -199,14 +214,16 @@ fn invoke_translate(args: &[ArrayRef]) -> Result<ArrayRef> {
 
 /// Replaces each character in string that matches a character in the from set with the corresponding character in the to set. If from is longer than to, occurrences of the extra characters in from are deleted.
 /// translate('12345', '143', 'ax') = 'a2x5'
-fn translate<'a, T: OffsetSizeTrait, V, B>(
+fn translate<'a, V, B, O>(
     string_array: V,
     from_array: B,
     to_array: B,
+    mut builder: O,
 ) -> Result<ArrayRef>
 where
     V: ArrayAccessor<Item = &'a str>,
     B: ArrayAccessor<Item = &'a str>,
+    O: StringLikeArrayBuilder,
 {
     let string_array_iter = ArrayIter::new(string_array);
     let from_array_iter = ArrayIter::new(from_array);
@@ -219,10 +236,9 @@ where
     let mut string_graphemes: Vec<&str> = Vec::new();
     let mut result_graphemes: Vec<&str> = Vec::new();
 
-    let result = string_array_iter
-        .zip(from_array_iter)
-        .zip(to_array_iter)
-        .map(|((string, from), to)| match (string, from, to) {
+    for ((string, from), to) in string_array_iter.zip(from_array_iter).zip(to_array_iter)
+    {
+        match (string, from, to) {
             (Some(string), Some(from), Some(to)) => {
                 // Clear and reuse buffers
                 from_map.clear();
@@ -254,13 +270,13 @@ where
                     }
                 }
 
-                Some(result_graphemes.concat())
+                builder.append_value(&result_graphemes.concat());
             }
-            _ => None,
-        })
-        .collect::<GenericStringArray<T>>();
+            _ => builder.append_null(),
+        }
+    }
 
-    Ok(Arc::new(result) as ArrayRef)
+    Ok(builder.finish())
 }
 
 /// Sentinel value in the ASCII translate table indicating the character should
@@ -300,21 +316,23 @@ fn build_ascii_translate_table(from: &str, to: &str) -> Option<[u8; 128]> {
 /// translation map instead of rebuilding it for every row.  When an ASCII byte
 /// lookup table is provided, ASCII input rows use the lookup table; non-ASCII
 /// inputs fallback to using the map.
-fn translate_with_map<'a, T: OffsetSizeTrait, V>(
+fn translate_with_map<'a, V, O>(
     string_array: V,
     from_map: &HashMap<&str, usize>,
     to_graphemes: &[&str],
     ascii_table: Option<&[u8; 128]>,
+    mut builder: O,
 ) -> Result<ArrayRef>
 where
     V: ArrayAccessor<Item = &'a str>,
+    O: StringLikeArrayBuilder,
 {
     let mut result_graphemes: Vec<&str> = Vec::new();
     let mut ascii_buf: Vec<u8> = Vec::new();
 
-    let result = ArrayIter::new(string_array)
-        .map(|string| {
-            string.map(|s| {
+    for string in ArrayIter::new(string_array) {
+        match string {
+            Some(s) => {
                 // Fast path: byte-level table lookup for ASCII strings
                 if let Some(table) = ascii_table
                     && s.is_ascii()
@@ -327,37 +345,38 @@ where
                         }
                     }
                     // SAFETY: all bytes are ASCII, hence valid UTF-8.
-                    return unsafe {
-                        std::str::from_utf8_unchecked(&ascii_buf).to_owned()
-                    };
-                }
-
-                // Slow path: grapheme-based translation
-                result_graphemes.clear();
-
-                for c in s.graphemes(true) {
-                    match from_map.get(c) {
-                        Some(n) => {
-                            if let Some(replacement) = to_graphemes.get(*n) {
-                                result_graphemes.push(*replacement);
+                    builder.append_value(unsafe {
+                        std::str::from_utf8_unchecked(&ascii_buf)
+                    });
+                } else {
+                    // Slow path: grapheme-based translation
+                    result_graphemes.clear();
+
+                    for c in s.graphemes(true) {
+                        match from_map.get(c) {
+                            Some(n) => {
+                                if let Some(replacement) = to_graphemes.get(*n) {
+                                    result_graphemes.push(*replacement);
+                                }
                             }
+                            None => result_graphemes.push(c),
                         }
-                        None => result_graphemes.push(c),
                     }
-                }
 
-                result_graphemes.concat()
-            })
-        })
-        .collect::<GenericStringArray<T>>();
+                    builder.append_value(&result_graphemes.concat());
+                }
+            }
+            None => builder.append_null(),
+        }
+    }
 
-    Ok(Arc::new(result) as ArrayRef)
+    Ok(builder.finish())
 }
 
 #[cfg(test)]
 mod tests {
-    use arrow::array::{Array, StringArray};
-    use arrow::datatypes::DataType::Utf8;
+    use arrow::array::{Array, StringArray, StringViewArray};
+    use arrow::datatypes::DataType::{Utf8, Utf8View};
 
     use datafusion_common::{Result, ScalarValue};
     use datafusion_expr::{ColumnarValue, ScalarUDFImpl};
@@ -453,6 +472,45 @@ mod tests {
             Utf8,
             StringArray
         );
+        // Utf8View input should produce Utf8View output
+        test_function!(
+            TranslateFunc::new(),
+            vec![
+                ColumnarValue::Scalar(ScalarValue::Utf8View(Some("12345".into()))),
+                ColumnarValue::Scalar(ScalarValue::from("143")),
+                ColumnarValue::Scalar(ScalarValue::from("ax"))
+            ],
+            Ok(Some("a2x5")),
+            &str,
+            Utf8View,
+            StringViewArray
+        );
+        // Null Utf8View input
+        test_function!(
+            TranslateFunc::new(),
+            vec![
+                ColumnarValue::Scalar(ScalarValue::Utf8View(None)),
+                ColumnarValue::Scalar(ScalarValue::from("143")),
+                ColumnarValue::Scalar(ScalarValue::from("ax"))
+            ],
+            Ok(None),
+            &str,
+            Utf8View,
+            StringViewArray
+        );
+        // Non-ASCII Utf8View input
+        test_function!(
+            TranslateFunc::new(),
+            vec![
+                ColumnarValue::Scalar(ScalarValue::Utf8View(Some("é2íñ5".into()))),
+                ColumnarValue::Scalar(ScalarValue::from("éñí")),
+                ColumnarValue::Scalar(ScalarValue::from("óü"))
+            ],
+            Ok(Some("ó2ü5")),
+            &str,
+            Utf8View,
+            StringViewArray
+        );
 
         #[cfg(not(feature = "unicode_expressions"))]
         test_function!(

datafusion/sqllogictest/test_files/string/string_literal.slt

@@ -1783,3 +1783,25 @@ SELECT
 ;
 ----
 48 176 32 40
+
+# translate preserves input string type
+
+query T
+SELECT translate(arrow_cast('12345', 'Utf8View'), '143', 'ax')
+----
+a2x5
+
+query T
+SELECT arrow_typeof(translate('12345', '143', 'ax'))
+----
+Utf8
+
+query T
+SELECT arrow_typeof(translate(arrow_cast('12345', 'LargeUtf8'), '143', 'ax'))
+----
+LargeUtf8
+
+query T
+SELECT arrow_typeof(translate(arrow_cast('12345', 'Utf8View'), '143', 'ax'))
+----
+Utf8View