parthchandra commented on code in PR #1680:
URL: https://github.com/apache/datafusion-comet/pull/1680#discussion_r2064867088


##########
native/spark-expr/src/array_funcs/array_repeat.rs:
##########
@@ -0,0 +1,216 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use arrow::array::{
+    new_null_array, Array, ArrayRef, Capacities, GenericListArray, ListArray, 
MutableArrayData,
+    NullBufferBuilder, OffsetSizeTrait, UInt64Array,
+};
+use arrow::buffer::OffsetBuffer;
+use arrow::compute;
+use arrow::compute::cast;
+use arrow::datatypes::DataType::{LargeList, List};
+use arrow::datatypes::{DataType, Field};
+use datafusion::common::cast::{as_large_list_array, as_list_array, 
as_uint64_array};
+use datafusion::common::{exec_err, DataFusionError, ScalarValue};
+use datafusion::logical_expr::ColumnarValue;
+use std::sync::Arc;
+
+pub fn make_scalar_function<F>(
+    inner: F,
+) -> impl Fn(&[ColumnarValue]) -> Result<ColumnarValue, DataFusionError>
+where
+    F: Fn(&[ArrayRef]) -> Result<ArrayRef, DataFusionError>,
+{
+    move |args: &[ColumnarValue]| {
+        // first, identify if any of the arguments is an Array. If yes, store 
its `len`,
+        // as any scalar will need to be converted to an array of len `len`.
+        let len = args
+            .iter()
+            .fold(Option::<usize>::None, |acc, arg| match arg {
+                ColumnarValue::Scalar(_) => acc,
+                ColumnarValue::Array(a) => Some(a.len()),
+            });
+
+        let is_scalar = len.is_none();
+
+        let args = ColumnarValue::values_to_arrays(args)?;
+
+        let result = (inner)(&args);
+
+        if is_scalar {
+            // If all inputs are scalar, keeps output as scalar
+            let result = result.and_then(|arr| 
ScalarValue::try_from_array(&arr, 0));
+            result.map(ColumnarValue::Scalar)
+        } else {
+            result.map(ColumnarValue::Array)
+        }
+    }
+}
+
+pub fn spark_array_repeat(args: &[ColumnarValue]) -> Result<ColumnarValue, 
DataFusionError> {
+    make_scalar_function(spark_array_repeat_inner)(args)
+}
+
+/// Array_repeat SQL function
+fn spark_array_repeat_inner(args: &[ArrayRef]) -> 
datafusion::common::Result<ArrayRef> {
+    let element = &args[0];
+    let count_array = &args[1];
+
+    let count_array = match count_array.data_type() {
+        DataType::Int64 => &cast(count_array, &DataType::UInt64)?,
+        DataType::UInt64 => count_array,
+        _ => return exec_err!("count must be an integer type"),
+    };
+
+    let count_array = as_uint64_array(count_array)?;
+
+    match element.data_type() {
+        List(_) => {
+            let list_array = as_list_array(element)?;
+            general_list_repeat::<i32>(list_array, count_array)
+        }
+        LargeList(_) => {
+            let list_array = as_large_list_array(element)?;
+            general_list_repeat::<i64>(list_array, count_array)
+        }
+        _ => general_repeat::<i32>(element, count_array),
+    }
+}
+
+/// For each element of `array[i]` repeat `count_array[i]` times.
+///
+/// Assumption for the input:
+///     1. `count[i] >= 0`
+///     2. `array.len() == count_array.len()`
+///
+/// For example,
+/// ```text
+/// array_repeat(
+///     [1, 2, 3], [2, 0, 1] => [[1, 1], [], [3]]
+/// )
+/// ```
+fn general_repeat<O: OffsetSizeTrait>(
+    array: &ArrayRef,
+    count_array: &UInt64Array,
+) -> datafusion::common::Result<ArrayRef> {
+    let data_type = array.data_type();
+    let mut new_values = vec![];
+
+    let count_vec = count_array
+        .values()
+        .to_vec()
+        .iter()
+        .map(|x| *x as usize)
+        .collect::<Vec<_>>();
+
+    let mut nulls = NullBufferBuilder::new(count_array.len());
+
+    for (row_index, &count) in count_vec.iter().enumerate() {
+        nulls.append(!count_array.is_null(row_index));
+        let repeated_array = if array.is_null(row_index) {

Review Comment:
   Should the result be a null array if the count is zero ?



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