Improve performance of trim for string view (10%) (#12395)

* draft.

* add unit tests for xTrim.

* fix fmt.

* tmp copy for ci.

* move `make_and_append_view` to common.

* fix sting view trim about the process of empty string.

* fix compile.

* eliminate some repeated codes.

* add sql test case about string view trim.

* remove unused imports.

* fix tests.

* remove stale file.

* Avoid unecessary unsafe

* add unit test cases with a unlined string view output.

* fix tests.

* improve comments.

* add todo and the related issue.

* use the safe way to get `start_offset` after trimming.

* fix comments.

* Remove redundant test

---------

Co-authored-by: Andrew Lamb <[email protected]>

Author: Rachelint

datafusion/functions/src/string/btrim.rs

@@ -82,7 +82,11 @@ impl ScalarUDFImpl for BTrimFunc {
     }
 
     fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
-        utf8_to_str_type(&arg_types[0], "btrim")
+        if arg_types[0] == DataType::Utf8View {
+            Ok(DataType::Utf8View)
+        } else {
+            utf8_to_str_type(&arg_types[0], "btrim")
+        }
     }
 
     fn invoke(&self, args: &[ColumnarValue]) -> Result<ColumnarValue> {
@@ -106,3 +110,149 @@ impl ScalarUDFImpl for BTrimFunc {
         &self.aliases
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use arrow::array::{Array, StringArray, StringViewArray};
+    use arrow::datatypes::DataType::{Utf8, Utf8View};
+
+    use datafusion_common::{Result, ScalarValue};
+    use datafusion_expr::{ColumnarValue, ScalarUDFImpl};
+
+    use crate::string::btrim::BTrimFunc;
+    use crate::utils::test::test_function;
+
+    #[test]
+    fn test_functions() {
+        // String view cases for checking normal logic
+        test_function!(
+            BTrimFunc::new(),
+            &[ColumnarValue::Scalar(ScalarValue::Utf8View(Some(
+                String::from("alphabet  ")
+            ))),],
+            Ok(Some("alphabet")),
+            &str,
+            Utf8View,
+            StringViewArray
+        );
+        test_function!(
+            BTrimFunc::new(),
+            &[ColumnarValue::Scalar(ScalarValue::Utf8View(Some(
+                String::from("  alphabet  ")
+            ))),],
+            Ok(Some("alphabet")),
+            &str,
+            Utf8View,
+            StringViewArray
+        );
+        test_function!(
+            BTrimFunc::new(),
+            &[
+                ColumnarValue::Scalar(ScalarValue::Utf8View(Some(String::from(
+                    "alphabet"
+                )))),
+                ColumnarValue::Scalar(ScalarValue::Utf8View(Some(String::from("t")))),
+            ],
+            Ok(Some("alphabe")),
+            &str,
+            Utf8View,
+            StringViewArray
+        );
+        test_function!(
+            BTrimFunc::new(),
+            &[
+                ColumnarValue::Scalar(ScalarValue::Utf8View(Some(String::from(
+                    "alphabet"
+                )))),
+                ColumnarValue::Scalar(ScalarValue::Utf8View(Some(String::from(
+                    "alphabe"
+                )))),
+            ],
+            Ok(Some("t")),
+            &str,
+            Utf8View,
+            StringViewArray
+        );
+        test_function!(
+            BTrimFunc::new(),
+            &[
+                ColumnarValue::Scalar(ScalarValue::Utf8View(Some(String::from(
+                    "alphabet"
+                )))),
+                ColumnarValue::Scalar(ScalarValue::Utf8View(None)),
+            ],
+            Ok(None),
+            &str,
+            Utf8View,
+            StringViewArray
+        );
+        // Special string view case for checking unlined output(len > 12)
+        test_function!(
+            BTrimFunc::new(),
+            &[
+                ColumnarValue::Scalar(ScalarValue::Utf8View(Some(String::from(
+                    "xxxalphabetalphabetxxx"
+                )))),
+                ColumnarValue::Scalar(ScalarValue::Utf8View(Some(String::from("x")))),
+            ],
+            Ok(Some("alphabetalphabet")),
+            &str,
+            Utf8View,
+            StringViewArray
+        );
+        // String cases
+        test_function!(
+            BTrimFunc::new(),
+            &[ColumnarValue::Scalar(ScalarValue::Utf8(Some(
+                String::from("alphabet  ")
+            ))),],
+            Ok(Some("alphabet")),
+            &str,
+            Utf8,
+            StringArray
+        );
+        test_function!(
+            BTrimFunc::new(),
+            &[ColumnarValue::Scalar(ScalarValue::Utf8(Some(
+                String::from("alphabet  ")
+            ))),],
+            Ok(Some("alphabet")),
+            &str,
+            Utf8,
+            StringArray
+        );
+        test_function!(
+            BTrimFunc::new(),
+            &[
+                ColumnarValue::Scalar(ScalarValue::Utf8(Some(String::from("alphabet")))),
+                ColumnarValue::Scalar(ScalarValue::Utf8(Some(String::from("t")))),
+            ],
+            Ok(Some("alphabe")),
+            &str,
+            Utf8,
+            StringArray
+        );
+        test_function!(
+            BTrimFunc::new(),
+            &[
+                ColumnarValue::Scalar(ScalarValue::Utf8(Some(String::from("alphabet")))),
+                ColumnarValue::Scalar(ScalarValue::Utf8(Some(String::from("alphabe")))),
+            ],
+            Ok(Some("t")),
+            &str,
+            Utf8,
+            StringArray
+        );
+        test_function!(
+            BTrimFunc::new(),
+            &[
+                ColumnarValue::Scalar(ScalarValue::Utf8(Some(String::from("alphabet")))),
+                ColumnarValue::Scalar(ScalarValue::Utf8(None)),
+            ],
+            Ok(None),
+            &str,
+            Utf8,
+            StringArray
+        );
+    }
+}