Implement native support StringView for REPEAT

Signed-off-by: Tai Le Manh <[email protected]>

Author: tlm365

datafusion/functions/src/string/repeat.rs

@@ -18,10 +18,10 @@
 use std::any::Any;
 use std::sync::Arc;
 
-use arrow::array::{ArrayRef, GenericStringArray, OffsetSizeTrait};
+use arrow::array::{ArrayRef, GenericStringArray, OffsetSizeTrait, StringArray};
 use arrow::datatypes::DataType;
 
-use datafusion_common::cast::{as_generic_string_array, as_int64_array};
+use datafusion_common::cast::{as_generic_string_array, as_int64_array, as_string_view_array};
 use datafusion_common::{exec_err, Result};
 use datafusion_expr::TypeSignature::*;
 use datafusion_expr::{ColumnarValue, Volatility};
@@ -45,7 +45,14 @@ impl RepeatFunc {
         use DataType::*;
         Self {
             signature: Signature::one_of(
-                vec![Exact(vec![Utf8, Int64]), Exact(vec![LargeUtf8, Int64])],
+                vec![
+                    // Planner attempts coercion to the target type starting with the most preferred candidate.
+                    // For example, given input `(Utf8View, Int64)`, it first tries coercing to `(Utf8View, Int64)`.
+                    // If that fails, it proceeds to `(Utf8, Int64)`.
+                    Exact(vec![Utf8View, Int64]),
+                    Exact(vec![Utf8, Int64]),
+                    Exact(vec![LargeUtf8, Int64]),
+                ],
                 Volatility::Immutable,
             ),
         }
@@ -71,9 +78,10 @@ impl ScalarUDFImpl for RepeatFunc {
 
     fn invoke(&self, args: &[ColumnarValue]) -> Result<ColumnarValue> {
         match args[0].data_type() {
+            DataType::Utf8View => make_scalar_function(repeat_utf8view, vec![])(args),
             DataType::Utf8 => make_scalar_function(repeat::<i32>, vec![])(args),
             DataType::LargeUtf8 => make_scalar_function(repeat::<i64>, vec![])(args),
-            other => exec_err!("Unsupported data type {other:?} for function repeat"),
+            other => exec_err!("Unsupported data type {other:?} for function repeat. Expected Utf8, Utf8View or LargeUtf8"),
         }
     }
 }
@@ -87,18 +95,35 @@ fn repeat<T: OffsetSizeTrait>(args: &[ArrayRef]) -> Result<ArrayRef> {
     let result = string_array
         .iter()
         .zip(number_array.iter())
-        .map(|(string, number)| match (string, number) {
-            (Some(string), Some(number)) if number >= 0 => {
-                Some(string.repeat(number as usize))
-            }
-            (Some(_), Some(_)) => Some("".to_string()),
-            _ => None,
-        })
+        .map(|(string, number)| repeat_common(string, number))
         .collect::<GenericStringArray<T>>();
 
     Ok(Arc::new(result) as ArrayRef)
 }
 
+fn repeat_utf8view(args: &[ArrayRef]) -> Result<ArrayRef> {
+    let string_view_array = as_string_view_array(&args[0])?;
+    let number_array = as_int64_array(&args[1])?;
+
+    let result = string_view_array
+        .iter()
+        .zip(number_array.iter())
+        .map(|(string, number)| repeat_common(string, number))
+        .collect::<StringArray>();
+
+    Ok(Arc::new(result) as ArrayRef)
+}
+
+fn repeat_common(string: Option<&str>, number: Option<i64>) -> Option<String> {
+    match (string, number) {
+        (Some(string), Some(number)) if number >= 0 => {
+            Some(string.repeat(number as usize))
+        }
+        (Some(_), Some(_)) => Some("".to_string()),
+        _ => None,
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use arrow::array::{Array, StringArray};
@@ -124,7 +149,6 @@ mod tests {
             Utf8,
             StringArray
         );
-
         test_function!(
             RepeatFunc::new(),
             &[
@@ -148,6 +172,40 @@ mod tests {
             StringArray
         );
 
+        test_function!(
+            RepeatFunc::new(),
+            &[
+                ColumnarValue::Scalar(ScalarValue::Utf8View(Some(String::from("Pg")))),
+                ColumnarValue::Scalar(ScalarValue::Int64(Some(4))),
+            ],
+            Ok(Some("PgPgPgPg")),
+            &str,
+            Utf8,
+            StringArray
+        );
+        test_function!(
+            RepeatFunc::new(),
+            &[
+                ColumnarValue::Scalar(ScalarValue::Utf8View(None)),
+                ColumnarValue::Scalar(ScalarValue::Int64(Some(4))),
+            ],
+            Ok(None),
+            &str,
+            Utf8,
+            StringArray
+        );
+        test_function!(
+            RepeatFunc::new(),
+            &[
+                ColumnarValue::Scalar(ScalarValue::Utf8View(Some(String::from("Pg")))),
+                ColumnarValue::Scalar(ScalarValue::Int64(None)),
+            ],
+            Ok(None),
+            &str,
+            Utf8,
+            StringArray
+        );
+
         Ok(())
     }
 }