Merge pull request rapidsai#19415 from rapidsai/branch-25.08

Forward-merge branch-25.08 into branch-25.10

Author: GPUtester

cpp/src/strings/extract/extract.cu

@@ -104,7 +104,9 @@ std::unique_ptr<table> extract(strings_column_view const& input,
 
   auto const d_strings = column_device_view::create(input.parent(), stream);
 
-  launch_for_each_kernel(extract_fn{*d_strings, d_indices}, *d_prog, input.size(), stream);
+  if (!input.is_empty()) {
+    launch_for_each_kernel(extract_fn{*d_strings, d_indices}, *d_prog, input.size(), stream);
+  }
 
   // build a result column for each group
   std::vector<std::unique_ptr<column>> results(groups);
@@ -161,6 +163,8 @@ std::unique_ptr<column> extract_single(strings_column_view const& input,
                                        rmm::cuda_stream_view stream,
                                        rmm::device_async_resource_ref mr)
 {
+  if (input.is_empty()) { return make_empty_column(type_id::STRING); }
+
   // create device object from regex_program
   auto d_prog = regex_device_builder::create_prog_device(prog, stream);
 

cpp/tests/strings/extract_tests.cpp

@@ -338,6 +338,24 @@ TEST_F(StringsExtractTests, Errors)
   EXPECT_THROW(cudf::strings::extract_all_record(sv, *prog), cudf::logic_error);
 }
 
+TEST_F(StringsExtractTests, EmptyInput)
+{
+  auto const input   = cudf::test::strings_column_wrapper();
+  auto const sv      = cudf::strings_column_view(input);
+  auto const pattern = std::string("(\\w+)");
+  auto const prog    = cudf::strings::regex_program::create(pattern);
+
+  auto rt = cudf::strings::extract(sv, *prog);
+  EXPECT_EQ(1, rt->num_columns());
+  EXPECT_EQ(0, rt->num_rows());
+
+  auto rl = cudf::strings::extract_all_record(sv, *prog);
+  EXPECT_EQ(0, rl->size());
+
+  auto rs = cudf::strings::extract_single(sv, *prog, 1);
+  EXPECT_EQ(0, rs->size());
+}
+
 TEST_F(StringsExtractTests, MediumRegex)
 {
   // This results in 95 regex instructions and falls in the 'medium' range.