jayzhan211 commented on code in PR #8744:
URL: https://github.com/apache/arrow-datafusion/pull/8744#discussion_r1446964517


##########
datafusion/physical-expr/src/array_expressions.rs:
##########
@@ -2611,6 +2618,95 @@ pub fn array_distinct(args: &[ArrayRef]) -> 
Result<ArrayRef> {
     }
 }
 
+/// array_resize SQL function
+pub fn array_resize(arg: &[ArrayRef]) -> Result<ArrayRef> {
+    if arg.len() < 2 || arg.len() > 3 {
+        return exec_err!("array_resize needs two or three arguments");
+    }
+
+    let new_len = as_int64_array(&arg[1])?;
+    let new_element = if arg.len() == 3 {
+        Some(arg[2].clone())
+    } else {
+        None
+    };
+
+    match &arg[0].data_type() {
+        DataType::List(field) => {
+            let array = as_list_array(&arg[0])?;
+            general_list_resize::<i32>(array, new_len, field, new_element)
+        }
+        DataType::LargeList(field) => {
+            let array = as_large_list_array(&arg[0])?;
+            general_list_resize::<i64>(array, new_len, field, new_element)
+        }
+        array_type => exec_err!("array_resize does not support type 
'{array_type:?}'."),
+    }
+}
+
+/// array_resize keep the original array and append the default element to the 
end
+fn general_list_resize<O: OffsetSizeTrait>(
+    array: &GenericListArray<O>,
+    count_array: &Int64Array,
+    field: &FieldRef,
+    default_element: Option<ArrayRef>,
+) -> Result<ArrayRef>
+where
+    O: TryInto<i64>,
+{
+    let mut default_element_array = vec![];
+
+    let data_type = array.value_type();
+    let default_element = if let Some(default_element) = default_element {
+        default_element
+    } else {
+        let null_scalar = ScalarValue::try_from(&data_type)?;
+        null_scalar.to_array_of_size(1)?
+    };
+
+    // create a mutable array to store the original data
+    let values = array.values();
+    let original_data = values.to_data();
+    let capacity = Capacities::Array(original_data.len());
+    let mut offsets = vec![O::usize_as(0)];
+    let mut mutable =
+        MutableArrayData::with_capacities(vec![&original_data], false, 
capacity);
+
+    for (row_index, offset_window) in array.offsets().windows(2).enumerate() {
+        let count = count_array.value(row_index).to_usize().ok_or_else(|| {
+            exec_datafusion_err!("array_resize: failed to convert size to 
usize")
+        })?;
+        let count = O::usize_as(count);
+        let start = offset_window[0];
+        let end = if start + count > offset_window[1] {
+            let value = (start + count - 
offset_window[1]).try_into().map_err(|_| {
+                exec_datafusion_err!("array_resize: failed to convert size to 
i64")
+            })?;
+            default_element_array.push(Some(value));
+            offset_window[1]
+        } else {
+            default_element_array.push(None);
+            start + count
+        };
+        mutable.extend(0, (start).to_usize().unwrap(), 
(end).to_usize().unwrap());
+        offsets.push(offsets[row_index] + end - start);
+    }
+
+    let default_element_array = 
Arc::new(Int64Array::from(default_element_array));
+    let default_element_array =
+        general_repeat::<O>(&default_element, &default_element_array)?;

Review Comment:
   repeat can be replaced with repeating extend() calls



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