chore: Cleanup code to use repeat_n in a few places (#20527)

## Which issue does this PR close?

N/A

## Rationale for this change

Using `repeat_n` is more readable and slightly faster than
`(0..n).map(|_| ...)`.

## What changes are included in this PR?

## Are these changes tested?

Yes.

## Are there any user-facing changes?

No.

Author: neilconway

datafusion/core/benches/spm.rs

@@ -66,10 +66,9 @@ fn generate_spm_for_round_robin_tie_breaker(
         RecordBatch::try_from_iter(vec![("a", a), ("b", b), ("c", c)]).unwrap()
     };
 
-    let rbs = (0..batch_count).map(|_| rb.clone()).collect::<Vec<_>>();
-    let partitions = vec![rbs.clone(); partition_count];
-
     let schema = rb.schema();
+    let rbs = std::iter::repeat_n(rb, batch_count).collect::<Vec<_>>();
+    let partitions = vec![rbs.clone(); partition_count];
     let sort = [
         PhysicalSortExpr {
             expr: col("b", &schema).unwrap(),

datafusion/core/tests/fuzz_cases/spilling_fuzz_in_memory_constrained_env.rs

@@ -278,9 +278,11 @@ async fn run_sort_test_with_limited_memory(
 
                     let string_item_size =
                         record_batch_memory_size / record_batch_size as usize;
-                    let string_array = Arc::new(StringArray::from_iter_values(
-                        (0..record_batch_size).map(|_| "a".repeat(string_item_size)),
-                    ));
+                    let string_array =
+                        Arc::new(StringArray::from_iter_values(std::iter::repeat_n(
+                            "a".repeat(string_item_size),
+                            record_batch_size as usize,
+                        )));
 
                     RecordBatch::try_new(
                         Arc::clone(&schema),
@@ -536,9 +538,11 @@ async fn run_test_aggregate_with_high_cardinality(
 
                     let string_item_size =
                         record_batch_memory_size / record_batch_size as usize;
-                    let string_array = Arc::new(StringArray::from_iter_values(
-                        (0..record_batch_size).map(|_| "a".repeat(string_item_size)),
-                    ));
+                    let string_array =
+                        Arc::new(StringArray::from_iter_values(std::iter::repeat_n(
+                            "a".repeat(string_item_size),
+                            record_batch_size as usize,
+                        )));
 
                     RecordBatch::try_new(
                         Arc::clone(&schema),

datafusion/physical-plan/src/async_func.rs

@@ -392,7 +392,7 @@ mod tests {
             vec![Arc::new(UInt32Array::from(vec![1, 2, 3, 4, 5, 6]))],
         )?;
 
-        let batches: Vec<RecordBatch> = (0..50).map(|_| batch.clone()).collect();
+        let batches: Vec<RecordBatch> = std::iter::repeat_n(batch, 50).collect();
 
         let session_config = SessionConfig::new().with_batch_size(200);
         let task_ctx = TaskContext::default().with_session_config(session_config);

datafusion/physical-plan/src/repartition/mod.rs

@@ -2483,7 +2483,7 @@ mod tests {
     /// Create vector batches
     fn create_vec_batches(n: usize) -> Vec<RecordBatch> {
         let batch = create_batch();
-        (0..n).map(|_| batch.clone()).collect()
+        std::iter::repeat_n(batch, n).collect()
     }
 
     /// Create batch

datafusion/physical-plan/src/sorts/sort_preserving_merge.rs

@@ -475,10 +475,9 @@ mod tests {
         let b: ArrayRef = Arc::new(StringArray::from_iter(vec![Some("a"); row_size]));
         let c: ArrayRef = Arc::new(Int64Array::from_iter(vec![0; row_size]));
         let rb = RecordBatch::try_from_iter(vec![("a", a), ("b", b), ("c", c)])?;
-
-        let rbs = (0..1024).map(|_| rb.clone()).collect::<Vec<_>>();
-
         let schema = rb.schema();
+
+        let rbs = std::iter::repeat_n(rb, 1024).collect::<Vec<_>>();
         let sort = [
             PhysicalSortExpr {
                 expr: col("b", &schema)?,

datafusion/spark/src/function/map/utils.rs

@@ -181,8 +181,8 @@ fn map_deduplicate_keys(
         let num_keys_entries = *next_keys_offset as usize - cur_keys_offset;
         let num_values_entries = *next_values_offset as usize - cur_values_offset;
 
-        let mut keys_mask_one = [false].repeat(num_keys_entries);
-        let mut values_mask_one = [false].repeat(num_values_entries);
+        let mut keys_mask_one = vec![false; num_keys_entries];
+        let mut values_mask_one = vec![false; num_values_entries];
 
         let key_is_valid = keys_nulls.is_none_or(|buf| buf.is_valid(row_idx));
         let value_is_valid = values_nulls.is_none_or(|buf| buf.is_valid(row_idx));