Add device_memory_resource parameter to create_string_vector_from_col…

…umn (rapidsai#10673)

Adds the `rmm::mr::device_memory_resource` parameter to the `cudf::strings::detail::create_string_vector_from_column` function. This will be called in a future API in a later PR and the resulting memory object will returned to the user.

Also found and removed a few related functions that are no longer necessary and updated the callers appropriately simplifying the logic there.

Authors:
  - David Wendt (https://github.com/davidwendt)

Approvers:
  - Nghia Truong (https://github.com/ttnghia)
  - Bradley Dice (https://github.com/bdice)

URL: rapidsai#10673

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

@@ -15,14 +15,13 @@
  */
 #pragma once
 
-#include <cudf/column/column.hpp>
-#include <cudf/column/column_device_view.cuh>
-#include <cudf/detail/null_mask.hpp>
-#include <cudf/strings/detail/utilities.cuh>
+#include <cudf/column/column_factories.hpp>
 #include <cudf/strings/detail/utilities.hpp>
 #include <cudf/strings/strings_column_view.hpp>
+#include <cudf/utilities/span.hpp>
 
 #include <rmm/cuda_stream_view.hpp>
+#include <rmm/device_uvector.hpp>
 #include <rmm/exec_policy.hpp>
 
 #include <thrust/scatter.h>
@@ -71,17 +70,9 @@ std::unique_ptr<column> scatter(
   // do the scatter
   thrust::scatter(rmm::exec_policy(stream), begin, end, scatter_map, target_vector.begin());
 
-  // build offsets column
-  auto offsets_column = child_offsets_from_string_vector(target_vector, stream, mr);
-  // build chars column
-  auto chars_column =
-    child_chars_from_string_vector(target_vector, offsets_column->view(), stream, mr);
-
-  return make_strings_column(target.size(),
-                             std::move(offsets_column),
-                             std::move(chars_column),
-                             UNKNOWN_NULL_COUNT,
-                             cudf::detail::copy_bitmask(target.parent(), stream, mr));
+  // build the output column
+  auto sv_span = cudf::device_span<string_view const>(target_vector);
+  return make_strings_column(sv_span, string_view{nullptr, 0}, stream, mr);
 }
 
 }  // namespace detail

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

@@ -71,28 +71,6 @@ std::unique_ptr<column> make_offsets_child_column(
   return offsets_column;
 }
 
-/**
- * @brief Creates an offsets column from a string_view iterator, and size.
- *
- * @tparam Iter Iterator type that returns string_view instances
- * @param strings_begin Iterator to the beginning of the string_view sequence
- * @param num_strings The number of string_view instances in the sequence
- * @param stream CUDA stream used for device memory operations and kernel launches.
- * @param mr Device memory resource used to allocate the returned column's device memory.
- * @return Child offsets column
- */
-template <typename Iter>
-std::unique_ptr<cudf::column> child_offsets_from_string_iterator(
-  Iter strings_begin,
-  cudf::size_type num_strings,
-  rmm::cuda_stream_view stream,
-  rmm::mr::device_memory_resource* mr = rmm::mr::get_current_device_resource())
-{
-  auto transformer = [] __device__(string_view v) { return v.size_bytes(); };
-  auto begin       = thrust::make_transform_iterator(strings_begin, transformer);
-  return make_offsets_child_column(begin, begin + num_strings, stream, mr);
-}
-
 /**
  * @brief Copies input string data into a buffer and increments the pointer by the number of bytes
  * copied.

cpp/include/cudf/strings/detail/utilities.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019-2021, NVIDIA CORPORATION.
+ * Copyright (c) 2019-2022, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -45,36 +45,11 @@ std::unique_ptr<column> create_chars_child_column(
  *
  * @param strings Strings column instance.
  * @param stream CUDA stream used for device memory operations and kernel launches.
+ * @param mr Device memory resource used to allocate the returned vector's device memory.
  * @return Device vector of string_views
  */
 rmm::device_uvector<string_view> create_string_vector_from_column(
-  cudf::strings_column_view const strings, rmm::cuda_stream_view stream = rmm::cuda_stream_default);
-
-/**
- * @brief Creates an offsets column from a string_view vector.
- *
- * @param strings Strings input data
- * @param stream CUDA stream used for device memory operations and kernel launches.
- * @param mr Device memory resource used to allocate the returned column's device memory.
- * @return Child offsets column
- */
-std::unique_ptr<cudf::column> child_offsets_from_string_vector(
-  cudf::device_span<string_view> strings,
-  rmm::cuda_stream_view stream        = rmm::cuda_stream_default,
-  rmm::mr::device_memory_resource* mr = rmm::mr::get_current_device_resource());
-
-/**
- * @brief Creates a chars column from a string_view vector.
- *
- * @param strings Strings input data
- * @param d_offsets Offsets vector for placing strings into column's memory.
- * @param stream CUDA stream used for device memory operations and kernel launches.
- * @param mr Device memory resource used to allocate the returned column's device memory.
- * @return Child chars column
- */
-std::unique_ptr<cudf::column> child_chars_from_string_vector(
-  cudf::device_span<string_view> strings,
-  column_view const& offsets,
+  cudf::strings_column_view const strings,
   rmm::cuda_stream_view stream        = rmm::cuda_stream_default,
   rmm::mr::device_memory_resource* mr = rmm::mr::get_current_device_resource());
 

cpp/src/lists/copying/scatter_helper.cu

@@ -21,8 +21,7 @@
 #include <cudf/lists/detail/copying.hpp>
 #include <cudf/lists/detail/scatter_helper.cuh>
 #include <cudf/strings/detail/utilities.cuh>
-#include <cudf/strings/detail/utilities.hpp>
-#include <cudf/strings/strings_column_view.hpp>
+#include <cudf/utilities/span.hpp>
 
 #include <thrust/binary_search.h>
 #include <thrust/distance.h>
@@ -253,39 +252,16 @@ struct list_child_constructor {
         auto lists_column    = actual_list_row.get_column();
         auto lists_offsets_ptr    = lists_column.offsets().template data<offset_type>();
         auto child_strings_column = lists_column.child();
-        auto string_offsets_ptr =
-          child_strings_column.child(cudf::strings_column_view::offsets_column_index)
-            .template data<offset_type>();
-        auto string_chars_ptr =
-          child_strings_column.child(cudf::strings_column_view::chars_column_index)
-            .template data<char>();
-
-        auto strings_offset = lists_offsets_ptr[row_index] + intra_index;
-        auto char_offset    = string_offsets_ptr[strings_offset];
-        auto char_ptr       = string_chars_ptr + char_offset;
-        auto string_size =
-          string_offsets_ptr[strings_offset + 1] - string_offsets_ptr[strings_offset];
-        return string_view{char_ptr, string_size};
+        auto strings_offset       = lists_offsets_ptr[row_index] + intra_index;
+
+        return child_strings_column.is_null(strings_offset)
+                 ? string_view{nullptr, 0}
+                 : child_strings_column.template element<string_view>(strings_offset);
       });
 
     // string_views should now have been populated with source and target references.
-
-    auto string_offsets = cudf::strings::detail::child_offsets_from_string_iterator(
-      string_views.begin(), string_views.size(), stream, mr);
-
-    auto string_chars = cudf::strings::detail::child_chars_from_string_vector(
-      string_views, string_offsets->view(), stream, mr);
-    auto child_null_mask =
-      source_lists_column_view.child().nullable() || target_lists_column_view.child().nullable()
-        ? construct_child_nullmask(
-            list_vector, list_offsets, source_lists, target_lists, num_child_rows, stream, mr)
-        : std::make_pair(rmm::device_buffer{}, 0);
-
-    return cudf::make_strings_column(num_child_rows,
-                                     std::move(string_offsets),
-                                     std::move(string_chars),
-                                     child_null_mask.second,  // Null count.
-                                     std::move(child_null_mask.first));
+    auto sv_span = cudf::device_span<string_view const>(string_views);
+    return cudf::make_strings_column(sv_span, string_view{nullptr, 0}, stream, mr);
   }
 
   /**

cpp/src/strings/utilities.cu

@@ -20,20 +20,15 @@
 
 #include <cudf/column/column_device_view.cuh>
 #include <cudf/column/column_factories.hpp>
-#include <cudf/detail/get_value.cuh>
 #include <cudf/strings/detail/utilities.cuh>
 #include <cudf/utilities/error.hpp>
 
 #include <rmm/cuda_stream_view.hpp>
 #include <rmm/device_uvector.hpp>
 #include <rmm/exec_policy.hpp>
 
-#include <thrust/for_each.h>
 #include <thrust/iterator/counting_iterator.h>
-#include <thrust/transform_reduce.h>
-#include <thrust/transform_scan.h>
-
-#include <cstring>
+#include <thrust/transform.h>
 
 namespace cudf {
 namespace strings {
@@ -42,65 +37,27 @@ namespace detail {
 /**
  * @copydoc create_string_vector_from_column
  */
-rmm::device_uvector<string_view> create_string_vector_from_column(cudf::strings_column_view strings,
-                                                                  rmm::cuda_stream_view stream)
-{
-  auto strings_column = column_device_view::create(strings.parent(), stream);
-  auto d_column       = *strings_column;
-
-  rmm::device_uvector<string_view> strings_vector(strings.size(), stream);
-  string_view* d_strings = strings_vector.data();
-  thrust::for_each_n(rmm::exec_policy(stream),
-                     thrust::make_counting_iterator<size_type>(0),
-                     strings.size(),
-                     [d_column, d_strings] __device__(size_type idx) {
-                       if (d_column.is_null(idx))
-                         d_strings[idx] = string_view(nullptr, 0);
-                       else
-                         d_strings[idx] = d_column.element<string_view>(idx);
-                     });
-  return strings_vector;
-}
-
-/**
- * @copydoc child_offsets_from_string_vector
- */
-std::unique_ptr<cudf::column> child_offsets_from_string_vector(
-  cudf::device_span<string_view> strings,
+rmm::device_uvector<string_view> create_string_vector_from_column(
+  cudf::strings_column_view const input,
   rmm::cuda_stream_view stream,
   rmm::mr::device_memory_resource* mr)
 {
-  return child_offsets_from_string_iterator(strings.begin(), strings.size(), stream, mr);
-}
+  auto d_strings = column_device_view::create(input.parent(), stream);
 
-/**
- * @copydoc child_chars_from_string_vector
- */
-std::unique_ptr<cudf::column> child_chars_from_string_vector(cudf::device_span<string_view> strings,
-                                                             column_view const& offsets,
-                                                             rmm::cuda_stream_view stream,
-                                                             rmm::mr::device_memory_resource* mr)
-{
-  auto const d_strings = strings.data();
-  auto const bytes     = cudf::detail::get_value<int32_t>(offsets, strings.size(), stream);
-  auto const d_offsets = offsets.data<int32_t>();
-
-  // create column
-  auto chars_column = create_chars_child_column(bytes, stream, mr);
-  // get it's view
-  auto d_chars = chars_column->mutable_view().data<char>();
-  thrust::for_each_n(rmm::exec_policy(stream),
-                     thrust::make_counting_iterator<size_type>(0),
-                     strings.size(),
-                     [d_strings, d_offsets, d_chars] __device__(size_type idx) {
-                       string_view const d_str = d_strings[idx];
-                       memcpy(d_chars + d_offsets[idx], d_str.data(), d_str.size_bytes());
-                     });
-
-  return chars_column;
+  auto strings_vector = rmm::device_uvector<string_view>(input.size(), stream, mr);
+
+  thrust::transform(
+    rmm::exec_policy(stream),
+    thrust::make_counting_iterator<size_type>(0),
+    thrust::make_counting_iterator<size_type>(input.size()),
+    strings_vector.begin(),
+    [d_strings = *d_strings] __device__(size_type idx) {
+      return d_strings.is_null(idx) ? string_view{nullptr, 0} : d_strings.element<string_view>(idx);
+    });
+
+  return strings_vector;
 }
 
-//
 std::unique_ptr<column> create_chars_child_column(cudf::size_type total_bytes,
                                                   rmm::cuda_stream_view stream,
                                                   rmm::mr::device_memory_resource* mr)