Add large-strings gtest for cudf::interleave_columns (#15669)

Adds a gtest for `cudf::interleave_columns` that tests it can produce large-strings appropriately.
Follow on to #15544

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

Approvers:
  - Yunsong Wang (https://github.com/PointKernel)
  - Vyas Ramasubramani (https://github.com/vyasr)
  - MithunR (https://github.com/mythrocks)

URL: #15669

cpp/tests/CMakeLists.txt

@@ -571,8 +571,12 @@ ConfigureTest(
 # ##################################################################################################
 # * large strings test ----------------------------------------------------------------------------
 ConfigureTest(
-  LARGE_STRINGS_TEST large_strings/large_strings_fixture.cpp large_strings/merge_tests.cpp
-  large_strings/concatenate_tests.cpp large_strings/parquet_tests.cpp
+  LARGE_STRINGS_TEST
+  large_strings/large_strings_fixture.cpp
+  large_strings/merge_tests.cpp
+  large_strings/concatenate_tests.cpp
+  large_strings/parquet_tests.cpp
+  large_strings/reshape_tests.cpp
   GPUS 1
   PERCENT 100
 )

cpp/tests/large_strings/reshape_tests.cpp

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2024, NVIDIA CORPORATION.
+ *
+ * Licensed 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.
+ */
+
+#include "large_strings_fixture.hpp"
+
+#include <cudf_test/column_utilities.hpp>
+
+#include <cudf/copying.hpp>
+#include <cudf/reshape.hpp>
+#include <cudf/strings/strings_column_view.hpp>
+#include <cudf/table/table_view.hpp>
+
+#include <vector>
+
+struct ReshapeTest : public cudf::test::StringsLargeTest {};
+
+TEST_F(ReshapeTest, InterleaveLargeStrings)
+{
+  auto const input = this->long_column();
+  auto input_views = std::vector<cudf::table_view>();
+  auto const view  = cudf::table_view({input});
+  std::vector<cudf::size_type> splits;
+  int const multiplier = 10;
+  for (int i = 0; i < multiplier; ++i) {  // 2500MB > 2GB
+    input_views.push_back(view);
+    splits.push_back(view.num_rows() * (i + 1));
+  }
+  splits.pop_back();  // remove last entry
+
+  auto result = cudf::interleave_columns(input_views);
+  auto sv     = cudf::strings_column_view(result->view());
+  EXPECT_EQ(sv.size(), view.num_rows() * multiplier);
+  EXPECT_EQ(sv.offsets().type(), cudf::data_type{cudf::type_id::INT64});
+
+  auto sliced = cudf::split(sv.parent(), splits);
+  for (auto c : sliced) {
+    CUDF_TEST_EXPECT_COLUMNS_EQUIVALENT(c, input);
+  }
+
+  // also check regular sizes returns 32-bit offsets
+  input_views.clear();
+  input_views.push_back(view);
+  input_views.push_back(view);
+  result = cudf::interleave_columns(input_views);
+  sv     = cudf::strings_column_view(result->view());
+  EXPECT_EQ(sv.size(), view.num_rows() * 2);
+  EXPECT_EQ(sv.offsets().type(), cudf::data_type{cudf::type_id::INT32});
+  sliced = cudf::split(sv.parent(), {view.num_rows()});
+  CUDF_TEST_EXPECT_COLUMNS_EQUIVALENT(sliced[0], input);
+  CUDF_TEST_EXPECT_COLUMNS_EQUIVALENT(sliced[1], input);
+}