Remove unneeded calls to create_chars_child_column utility

cpp/include/cudf/strings/detail/gather.cuh

@@ -222,19 +222,19 @@ CUDF_KERNEL void gather_chars_fn_char_parallel(StringIterator strings_begin,
  * @return New chars column fit for a strings column.
  */
 template <typename StringIterator, typename MapIterator>
-std::unique_ptr<cudf::column> gather_chars(StringIterator strings_begin,
-                                           MapIterator map_begin,
-                                           MapIterator map_end,
-                                           cudf::detail::input_offsetalator const offsets,
-                                           size_type chars_bytes,
-                                           rmm::cuda_stream_view stream,
-                                           rmm::mr::device_memory_resource* mr)
+rmm::device_uvector<char> gather_chars(StringIterator strings_begin,
+                                       MapIterator map_begin,
+                                       MapIterator map_end,
+                                       cudf::detail::input_offsetalator const offsets,
+                                       size_type chars_bytes,
+                                       rmm::cuda_stream_view stream,
+                                       rmm::mr::device_memory_resource* mr)
 {
   auto const output_count = std::distance(map_begin, map_end);
-  if (output_count == 0) return make_empty_column(type_id::INT8);
+  if (output_count == 0) return rmm::device_uvector<char>(0, stream, mr);
 
-  auto chars_column  = create_chars_child_column(chars_bytes, stream, mr);
-  auto const d_chars = chars_column->mutable_view().template data<char>();
+  auto chars_data = rmm::device_uvector<char>(chars_bytes, stream, mr);
+  auto d_chars    = chars_data.data();
 
   constexpr int warps_per_threadblock = 4;
   // String parallel strategy will be used if average string length is above this threshold.
@@ -260,7 +260,7 @@ std::unique_ptr<cudf::column> gather_chars(StringIterator strings_begin,
          stream.value()>>>(strings_begin, d_chars, offsets, map_begin, output_count);
   }
 
-  return chars_column;
+  return chars_data;
 }
 
 /**
@@ -316,12 +316,12 @@ std::unique_ptr<cudf::column> gather(strings_column_view const& strings,
   // build chars column
   auto const offsets_view =
     cudf::detail::offsetalator_factory::make_input_iterator(out_offsets_column->view());
-  auto out_chars_column = gather_chars(
+  auto out_chars_data = gather_chars(
     d_strings->begin<string_view>(), begin, end, offsets_view, total_bytes, stream, mr);
 
   return make_strings_column(output_count,
                              std::move(out_offsets_column),
-                             std::move(out_chars_column->release().data.release()[0]),
+                             out_chars_data.release(),
                              0,  // caller sets these
                              rmm::device_buffer{});
 }

cpp/include/cudf/strings/detail/strings_column_factories.cuh

@@ -98,46 +98,44 @@ std::unique_ptr<column> make_strings_column(IndexPairIterator begin,
     (null_count > 0) ? std::move(new_nulls.first) : rmm::device_buffer{0, stream, mr};
 
   // build chars column
-  std::unique_ptr<column> chars_column =
-    [offsets_view, bytes = bytes, begin, strings_count, null_count, stream, mr] {
-      auto const avg_bytes_per_row = bytes / std::max(strings_count - null_count, 1);
-      // use a character-parallel kernel for long string lengths
-      if (avg_bytes_per_row > FACTORY_BYTES_PER_ROW_THRESHOLD) {
-        auto const d_offsets =
-          cudf::detail::offsetalator_factory::make_input_iterator(offsets_view);
-        auto const str_begin = thrust::make_transform_iterator(
-          begin, cuda::proclaim_return_type<string_view>([] __device__(auto ip) {
-            return string_view{ip.first, ip.second};
-          }));
-
-        return gather_chars(str_begin,
-                            thrust::make_counting_iterator<size_type>(0),
-                            thrust::make_counting_iterator<size_type>(strings_count),
-                            d_offsets,
-                            bytes,
-                            stream,
-                            mr);
-      } else {
-        // this approach is 2-3x faster for a large number of smaller string lengths
-        auto chars_column = create_chars_child_column(bytes, stream, mr);
-        auto d_chars      = chars_column->mutable_view().template data<char>();
-        auto copy_chars   = [d_chars] __device__(auto item) {
-          string_index_pair const str = thrust::get<0>(item);
-          size_type const offset      = thrust::get<1>(item);
-          if (str.first != nullptr) memcpy(d_chars + offset, str.first, str.second);
-        };
-        thrust::for_each_n(rmm::exec_policy(stream),
-                           thrust::make_zip_iterator(
-                             thrust::make_tuple(begin, offsets_view.template begin<int32_t>())),
-                           strings_count,
-                           copy_chars);
-        return chars_column;
-      }
-    }();
+  auto chars_data = [offsets_view, bytes = bytes, begin, strings_count, null_count, stream, mr] {
+    auto const avg_bytes_per_row = bytes / std::max(strings_count - null_count, 1);
+    // use a character-parallel kernel for long string lengths
+    if (avg_bytes_per_row > FACTORY_BYTES_PER_ROW_THRESHOLD) {
+      auto const d_offsets = cudf::detail::offsetalator_factory::make_input_iterator(offsets_view);
+      auto const str_begin = thrust::make_transform_iterator(
+        begin, cuda::proclaim_return_type<string_view>([] __device__(auto ip) {
+          return string_view{ip.first, ip.second};
+        }));
+
+      return gather_chars(str_begin,
+                          thrust::make_counting_iterator<size_type>(0),
+                          thrust::make_counting_iterator<size_type>(strings_count),
+                          d_offsets,
+                          bytes,
+                          stream,
+                          mr);
+    } else {
+      // this approach is 2-3x faster for a large number of smaller string lengths
+      auto chars_data = rmm::device_uvector<char>(bytes, stream, mr);
+      auto d_chars    = chars_data.data();
+      auto copy_chars = [d_chars] __device__(auto item) {
+        string_index_pair const str = thrust::get<0>(item);
+        size_type const offset      = thrust::get<1>(item);
+        if (str.first != nullptr) memcpy(d_chars + offset, str.first, str.second);
+      };
+      thrust::for_each_n(rmm::exec_policy(stream),
+                         thrust::make_zip_iterator(
+                           thrust::make_tuple(begin, offsets_view.template begin<int32_t>())),
+                         strings_count,
+                         copy_chars);
+      return chars_data;
+    }
+  }();
 
   return make_strings_column(strings_count,
                              std::move(offsets_column),
-                             std::move(chars_column->release().data.release()[0]),
+                             chars_data.release(),
                              null_count,
                              std::move(null_mask));
 }

cpp/src/io/csv/durations.cu

@@ -17,6 +17,7 @@
 #include <cudf/column/column_factories.hpp>
 #include <cudf/detail/null_mask.hpp>
 #include <cudf/detail/nvtx/ranges.hpp>
+#include <cudf/detail/offsets_iterator_factory.cuh>
 #include <cudf/strings/detail/convert/int_to_string.cuh>
 #include <cudf/strings/detail/strings_children.cuh>
 #include <cudf/strings/detail/utilities.cuh>
@@ -88,12 +89,12 @@ struct duration_to_string_size_fn {
 
 template <typename T>
 struct duration_to_string_fn : public duration_to_string_size_fn<T> {
-  int32_t const* d_offsets;
+  cudf::detail::input_offsetalator d_offsets;
   char* d_chars;
   using duration_to_string_size_fn<T>::d_durations;
 
   duration_to_string_fn(column_device_view const d_durations,
-                        int32_t const* d_offsets,
+                        cudf::detail::input_offsetalator d_offsets,
                         char* d_chars)
     : duration_to_string_size_fn<T>{d_durations}, d_offsets(d_offsets), d_chars(d_chars)
   {
@@ -181,28 +182,27 @@ struct dispatch_from_durations_fn {
 
     // copy null mask
     rmm::device_buffer null_mask = cudf::detail::copy_bitmask(durations, stream, mr);
+
     // build offsets column
-    auto offsets_transformer_itr = thrust::make_transform_iterator(
-      thrust::make_counting_iterator<int32_t>(0), duration_to_string_size_fn<T>{d_column});
-    auto [offsets_column, chars_bytes] = cudf::detail::make_offsets_child_column(
+    auto offsets_transformer_itr =
+      cudf::detail::make_counting_transform_iterator(0, duration_to_string_size_fn<T>{d_column});
+    auto [offsets_column, chars_bytes] = cudf::strings::detail::make_offsets_child_column(
       offsets_transformer_itr, offsets_transformer_itr + strings_count, stream, mr);
-    auto offsets_view  = offsets_column->view();
-    auto d_new_offsets = offsets_view.template data<int32_t>();
+    auto d_new_offsets =
+      cudf::detail::offsetalator_factory::make_input_iterator(offsets_column->view());
 
     // build chars column
-    auto chars_column = strings::detail::create_chars_child_column(chars_bytes, stream, mr);
-    auto chars_view   = chars_column->mutable_view();
-    auto d_chars      = chars_view.template data<char>();
+    auto chars_data = rmm::device_uvector<char>(chars_bytes, stream, mr);
+    auto d_chars    = chars_data.data();
 
     thrust::for_each_n(rmm::exec_policy(stream),
                        thrust::make_counting_iterator<size_type>(0),
                        strings_count,
                        duration_to_string_fn<T>{d_column, d_new_offsets, d_chars});
 
-    //
     return make_strings_column(strings_count,
                                std::move(offsets_column),
-                               std::move(chars_column->release().data.release()[0]),
+                               chars_data.release(),
                                durations.null_count(),
                                std::move(null_mask));
   }