[GitHub] [arrow] pitrou commented on a change in pull request #10585: ARROW-12016 [C++] Implement array_sort_indices and sort_indices for BOOL type

[GitBox <gi...@apache.org>]

pitrou commented on a change in pull request #10585:
URL: https://github.com/apache/arrow/pull/10585#discussion_r663999228



##########
File path: cpp/src/arrow/compute/kernels/vector_sort.cc
##########
@@ -477,6 +491,87 @@ class ArrayCountSorter {
   }
 };
 
+using ::arrow::internal::Bitmap;
+
+template <>
+class ArrayCountSorter<BooleanType> {
+ public:
+  ArrayCountSorter() = default;
+
+  // Returns where null starts.
+  uint64_t* Sort(uint64_t* indices_begin, uint64_t* indices_end,
+                 const BooleanArray& values, int64_t offset,
+                 const ArraySortOptions& options) {
+    // 32bit counter performs much better than 64bit one

Review comment:
       This sounds rather weird. Are you sure about this?

##########
File path: cpp/src/arrow/compute/kernels/vector_sort.cc
##########
@@ -477,6 +491,87 @@ class ArrayCountSorter {
   }
 };
 
+using ::arrow::internal::Bitmap;
+
+template <>
+class ArrayCountSorter<BooleanType> {
+ public:
+  ArrayCountSorter() = default;
+
+  // Returns where null starts.
+  uint64_t* Sort(uint64_t* indices_begin, uint64_t* indices_end,
+                 const BooleanArray& values, int64_t offset,
+                 const ArraySortOptions& options) {
+    // 32bit counter performs much better than 64bit one
+    if (values.length() < (1LL << 32)) {
+      return SortInternal<uint32_t>(indices_begin, indices_end, values, offset, options);
+    } else {
+      return SortInternal<uint64_t>(indices_begin, indices_end, values, offset, options);
+    }
+  }
+
+ private:
+  template <typename CounterType>
+  void CountBits(const BooleanArray& values, int64_t offset, CounterType* set_count,
+                 CounterType* null_count) {

Review comment:
       Really, you needn't write this yourself. Just call `null_count()` and `true_count()`.

##########
File path: cpp/src/arrow/compute/kernels/vector_sort_test.cc
##########
@@ -980,6 +1056,68 @@ TEST_F(TestTableSortIndices, NaNAndNull) {
   AssertSortIndices(table, options, "[7, 1, 2, 6, 5, 4, 0, 3]");
 }
 
+TEST_F(TestTableSortIndices, Boolean) {

Review comment:
       Same here.

##########
File path: cpp/src/arrow/compute/kernels/vector_sort_test.cc
##########
@@ -842,6 +877,47 @@ TEST_F(TestRecordBatchSortIndices, NaNAndNull) {
   AssertSortIndices(batch, options, "[7, 1, 2, 6, 5, 4, 0, 3]");
 }
 
+TEST_F(TestRecordBatchSortIndices, Boolean) {

Review comment:
       I don't think it's worth testing the non-null case separately. This will make less test code to maintain.




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