Pass column names to write_csv instead of table_metadata pointer

cpp/include/cudf/io/csv.hpp

@@ -1338,8 +1338,8 @@ class csv_writer_options {
   std::string _true_value = std::string{"true"};
   // string to use for values == 0 in INT8 types (default 'false')
   std::string _false_value = std::string{"false"};
-  // Optional associated metadata
-  table_metadata const* _metadata = nullptr;
+  // Names of all columns; if empty, writer will generate column names
+  std::vector<std::string> _names;
 
   /**
    * @brief Constructor from sink and table.
@@ -1387,11 +1387,11 @@ class csv_writer_options {
   [[nodiscard]] table_view const& get_table() const { return _table; }
 
   /**
-   * @brief Returns optional associated metadata.
+   * @brief Returns names of the columns.
    *
-   * @return Optional associated metadata
+   * @return Names of the columns in the output file
    */
-  [[nodiscard]] table_metadata const* get_metadata() const { return _metadata; }
+  [[nodiscard]] std::vector<std::string> const& get_names() const { return _names; }
 
   /**
    * @brief Returns string to used for null entries.
@@ -1444,11 +1444,11 @@ class csv_writer_options {
 
   // Setter
   /**
-   * @brief Sets optional associated metadata.
+   * @brief Sets optional associated column names.
    *
-   @param metadata Associated metadata
+   @param names Associated column names
    */
-  void set_metadata(table_metadata* metadata) { _metadata = metadata; }
+  void set_names(std::vector<std::string> names) { _names = std::move(names); }
 
   /**
    * @brief Sets string to used for null entries.
@@ -1526,14 +1526,14 @@ class csv_writer_options_builder {
   }
 
   /**
-   * @brief Sets optional associated metadata.
+   * @brief Sets optional column names.
    *
-   * @param metadata Associated metadata
+   * @param names Column names
    * @return this for chaining
    */
-  csv_writer_options_builder& metadata(table_metadata* metadata)
+  csv_writer_options_builder& names(std::vector<std::string> names)
   {
-    options._metadata = metadata;
+    options._names = names;
     return *this;
   }
 

cpp/include/cudf/io/detail/csv.hpp

@@ -46,14 +46,14 @@ table_with_metadata read_csv(std::unique_ptr<cudf::io::datasource>&& source,
  *
  * @param sink Output sink
  * @param table The set of columns
- * @param metadata The metadata associated with the table
+ * @param column_names Column names for the output CSV
  * @param options Settings for controlling behavior
  * @param stream CUDA stream used for device memory operations and kernel launches.
  * @param mr Device memory resource to use for device memory allocation
  */
 void write_csv(data_sink* sink,
                table_view const& table,
-               const table_metadata* metadata,
+               host_span<std::string const> column_names,
                csv_writer_options const& options,
                rmm::cuda_stream_view stream,
                rmm::mr::device_memory_resource* mr = rmm::mr::get_current_device_resource());

cpp/src/io/csv/writer_impl.cu

@@ -279,21 +279,21 @@ struct column_to_strings_fn {
 //
 void write_chunked_begin(data_sink* out_sink,
                          table_view const& table,
-                         table_metadata const* metadata,
+                         host_span<std::string const> user_column_names,
                          csv_writer_options const& options,
                          rmm::cuda_stream_view stream,
                          rmm::mr::device_memory_resource* mr)
 {
   if (options.is_enabled_include_header()) {
-    // need to generate column names if metadata is not provided
+    // need to generate column names if names are not provided
     std::vector<std::string> generated_col_names;
-    if (metadata == nullptr) {
+    if (user_column_names.empty()) {
       generated_col_names.resize(table.num_columns());
       thrust::tabulate(generated_col_names.begin(), generated_col_names.end(), [](auto idx) {
         return std::to_string(idx);
       });
     }
-    auto const& column_names = (metadata == nullptr) ? generated_col_names : metadata->column_names;
+    auto const& column_names = user_column_names.empty() ? generated_col_names : user_column_names;
     CUDF_EXPECTS(column_names.size() == static_cast<size_t>(table.num_columns()),
                  "Mismatch between number of column headers and table columns.");
 
@@ -346,7 +346,6 @@ void write_chunked_begin(data_sink* out_sink,
 
 void write_chunked(data_sink* out_sink,
                    strings_column_view const& str_column_view,
-                   table_metadata const* metadata,
                    csv_writer_options const& options,
                    rmm::cuda_stream_view stream,
                    rmm::mr::device_memory_resource* mr)
@@ -399,15 +398,15 @@ void write_chunked(data_sink* out_sink,
 
 void write_csv(data_sink* out_sink,
                table_view const& table,
-               table_metadata const* metadata,
+               host_span<std::string const> user_column_names,
                csv_writer_options const& options,
                rmm::cuda_stream_view stream,
                rmm::mr::device_memory_resource* mr)
 {
   // write header: column names separated by delimiter:
   // (even for tables with no rows)
   //
-  write_chunked_begin(out_sink, table, metadata, options, stream, mr);
+  write_chunked_begin(out_sink, table, user_column_names, options, stream, mr);
 
   if (table.num_rows() > 0) {
     // no need to check same-size columns constraint; auto-enforced by table_view
@@ -476,7 +475,7 @@ void write_csv(data_sink* out_sink,
         return cudf::strings::detail::replace_nulls(str_table_view.column(0), narep, stream);
       }();
 
-      write_chunked(out_sink, str_concat_col->view(), metadata, options, stream, mr);
+      write_chunked(out_sink, str_concat_col->view(), options, stream, mr);
     }
   }
 }

cpp/src/io/functions.cpp

@@ -231,7 +231,7 @@ void write_csv(csv_writer_options const& options, rmm::mr::device_memory_resourc
   return csv::write_csv(  //
     sinks[0].get(),
     options.get_table(),
-    options.get_metadata(),
+    options.get_names(),
     options,
     cudf::get_default_stream(),
     mr);

cpp/tests/io/csv_test.cpp

@@ -277,30 +277,12 @@ void expect_column_data_equal(std::vector<T> const& lhs, cudf::column_view const
 
 void write_csv_helper(std::string const& filename,
                       cudf::table_view const& table,
-                      bool include_header,
                       std::vector<std::string> const& names = {})
 {
-  // csv_writer_options only keeps a pointer to metadata (non-owning)
-  cudf::io::table_metadata metadata{};
-
-  if (not names.empty()) {
-    metadata.column_names = names;
-  } else {
-    // generate some dummy column names
-    int i                  = 0;
-    auto const num_columns = table.num_columns();
-    metadata.column_names.reserve(num_columns);
-    std::generate_n(std::back_inserter(metadata.column_names), num_columns, [&i]() {
-      return std::string("col") + std::to_string(i++);
-    });
-  }
-
   cudf::io::csv_writer_options writer_options =
     cudf::io::csv_writer_options::builder(cudf::io::sink_info(filename), table)
-      .include_header(include_header)
-      .rows_per_chunk(
-        1)  // Note: this gets adjusted to multiple of 8 (per legacy code logic and requirements)
-      .metadata(&metadata);
+      .include_header(not names.empty())
+      .names(names);
 
   cudf::io::write_csv(writer_options);
 }
@@ -1509,7 +1491,7 @@ TYPED_TEST(CsvReaderNumericTypeTest, SingleColumnWithWriter)
 
   auto filepath = temp_env->get_temp_filepath("SingleColumnWithWriter.csv");
 
-  write_csv_helper(filepath, input_table, false);
+  write_csv_helper(filepath, input_table);
 
   cudf::io::csv_reader_options in_opts =
     cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath}).header(-1);
@@ -1577,7 +1559,7 @@ TEST_F(CsvReaderTest, MultiColumnWithWriter)
 
   auto filepath = temp_env->get_temp_dir() + "MultiColumnWithWriter.csv";
 
-  write_csv_helper(filepath, input_table, false);
+  write_csv_helper(filepath, input_table);
 
   cudf::io::csv_reader_options in_opts =
     cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath})
@@ -1625,7 +1607,7 @@ TEST_F(CsvReaderTest, DatesWithWriter)
   cudf::table_view input_table(std::vector<cudf::column_view>{input_column});
 
   // TODO need to add a dayfirst flag?
-  write_csv_helper(filepath, input_table, false);
+  write_csv_helper(filepath, input_table);
 
   cudf::io::csv_reader_options in_opts =
     cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath})
@@ -1650,7 +1632,7 @@ TEST_F(CsvReaderTest, DatesStringWithWriter)
 
     cudf::table_view input_table(std::vector<cudf::column_view>{input_column});
 
-    write_csv_helper(filepath, input_table, false);
+    write_csv_helper(filepath, input_table);
 
     cudf::io::csv_reader_options in_opts =
       cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath})
@@ -1673,7 +1655,7 @@ TEST_F(CsvReaderTest, DatesStringWithWriter)
 
     cudf::table_view input_table(std::vector<cudf::column_view>{input_column});
 
-    write_csv_helper(filepath, input_table, false);
+    write_csv_helper(filepath, input_table);
 
     cudf::io::csv_reader_options in_opts =
       cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath})
@@ -1696,7 +1678,7 @@ TEST_F(CsvReaderTest, DatesStringWithWriter)
 
     cudf::table_view input_table(std::vector<cudf::column_view>{input_column});
 
-    write_csv_helper(filepath, input_table, false);
+    write_csv_helper(filepath, input_table);
 
     cudf::io::csv_reader_options in_opts =
       cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath})
@@ -1720,7 +1702,7 @@ TEST_F(CsvReaderTest, DatesStringWithWriter)
 
     cudf::table_view input_table(std::vector<cudf::column_view>{input_column});
 
-    write_csv_helper(filepath, input_table, false);
+    write_csv_helper(filepath, input_table);
 
     cudf::io::csv_reader_options in_opts =
       cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath})
@@ -1743,7 +1725,7 @@ TEST_F(CsvReaderTest, DatesStringWithWriter)
 
     cudf::table_view input_table(std::vector<cudf::column_view>{input_column});
 
-    write_csv_helper(filepath, input_table, false);
+    write_csv_helper(filepath, input_table);
 
     cudf::io::csv_reader_options in_opts =
       cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath})
@@ -1766,7 +1748,7 @@ TEST_F(CsvReaderTest, FloatingPointWithWriter)
   cudf::table_view input_table(std::vector<cudf::column_view>{input_column});
 
   // TODO add lineterminator=";"
-  write_csv_helper(filepath, input_table, false);
+  write_csv_helper(filepath, input_table);
 
   cudf::io::csv_reader_options in_opts =
     cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath})
@@ -1792,18 +1774,18 @@ TEST_F(CsvReaderTest, StringsWithWriter)
   cudf::table_view input_table(std::vector<cudf::column_view>{int_column, string_column});
 
   // TODO add quoting style flag?
-  write_csv_helper(filepath, input_table, true, names);
+  write_csv_helper(filepath, input_table, names);
 
   cudf::io::csv_reader_options in_opts =
     cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath})
-      .names(names)
       .dtypes(std::vector<data_type>{dtype<int32_t>(), dtype<cudf::string_view>()})
       .quoting(cudf::io::quote_style::NONE);
   auto result = cudf::io::read_csv(in_opts);
 
   const auto result_table = result.tbl->view();
   CUDF_TEST_EXPECT_COLUMNS_EQUIVALENT(input_table.column(0), result_table.column(0));
   check_string_column(input_table.column(1), result_table.column(1));
+  ASSERT_EQ(names, result.metadata.column_names);
 }
 
 TEST_F(CsvReaderTest, StringsWithWriterSimple)
@@ -1817,18 +1799,18 @@ TEST_F(CsvReaderTest, StringsWithWriterSimple)
   cudf::table_view input_table(std::vector<cudf::column_view>{int_column, string_column});
 
   // TODO add quoting style flag?
-  write_csv_helper(filepath, input_table, true, names);
+  write_csv_helper(filepath, input_table, names);
 
   cudf::io::csv_reader_options in_opts =
     cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath})
-      .names(names)
       .dtypes(std::vector<data_type>{dtype<int32_t>(), dtype<cudf::string_view>()})
       .quoting(cudf::io::quote_style::NONE);
   auto result = cudf::io::read_csv(in_opts);
 
   const auto result_table = result.tbl->view();
   CUDF_TEST_EXPECT_COLUMNS_EQUIVALENT(input_table.column(0), result_table.column(0));
   check_string_column(input_table.column(1), result_table.column(1));
+  ASSERT_EQ(names, result.metadata.column_names);
 }
 
 TEST_F(CsvReaderTest, StringsEmbeddedDelimiter)
@@ -1841,15 +1823,15 @@ TEST_F(CsvReaderTest, StringsEmbeddedDelimiter)
   auto string_column = column_wrapper<cudf::string_view>{"abc def ghi", "jkl,mno,pq", "stu vwx y"};
   cudf::table_view input_table(std::vector<cudf::column_view>{int_column, string_column});
 
-  write_csv_helper(filepath, input_table, true, names);
+  write_csv_helper(filepath, input_table, names);
 
   cudf::io::csv_reader_options in_opts =
     cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath})
-      .names(names)
       .dtypes(std::vector<data_type>{dtype<int32_t>(), dtype<cudf::string_view>()});
   auto result = cudf::io::read_csv(in_opts);
 
   CUDF_TEST_EXPECT_TABLES_EQUIVALENT(input_table, result.tbl->view());
+  ASSERT_EQ(names, result.metadata.column_names);
 }
 
 TEST_F(CsvReaderTest, HeaderEmbeddedDelimiter)
@@ -1864,7 +1846,7 @@ TEST_F(CsvReaderTest, HeaderEmbeddedDelimiter)
   cudf::table_view input_table(
     std::vector<cudf::column_view>{int_column, string_column, int_column, int_column, int_column});
 
-  write_csv_helper(filepath, input_table, true, names);
+  write_csv_helper(filepath, input_table, names);
 
   cudf::io::csv_reader_options in_opts =
     cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath})
@@ -1877,14 +1859,15 @@ TEST_F(CsvReaderTest, HeaderEmbeddedDelimiter)
   auto result = cudf::io::read_csv(in_opts);
 
   CUDF_TEST_EXPECT_TABLES_EQUIVALENT(input_table, result.tbl->view());
+  ASSERT_EQ(names, result.metadata.column_names);
 }
 
 TEST_F(CsvReaderTest, EmptyFileWithWriter)
 {
   auto filepath = temp_env->get_temp_dir() + "EmptyFileWithWriter.csv";
 
   cudf::table_view empty_table;
-  write_csv_helper(filepath, empty_table, false);
+  write_csv_helper(filepath, empty_table);
   cudf::io::csv_reader_options in_opts =
     cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath});
   auto result = cudf::io::read_csv(in_opts);
@@ -1968,7 +1951,7 @@ TEST_F(CsvReaderTest, DurationsWithWriter)
     durations_D, durations_s, durations_ms, durations_us, durations_ns});
   std::vector<std::string> names{"D", "s", "ms", "us", "ns"};
 
-  write_csv_helper(filepath, input_table, true, names);
+  write_csv_helper(filepath, input_table, names);
 
   cudf::io::csv_reader_options in_opts =
     cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath})
@@ -1982,6 +1965,7 @@ TEST_F(CsvReaderTest, DurationsWithWriter)
 
   const auto result_table = result.tbl->view();
   CUDF_TEST_EXPECT_TABLES_EQUIVALENT(input_table, result_table);
+  ASSERT_EQ(names, result.metadata.column_names);
 }
 
 TEST_F(CsvReaderTest, ParseInRangeIntegers)
@@ -2044,7 +2028,7 @@ TEST_F(CsvReaderTest, ParseInRangeIntegers)
 
   auto filepath = temp_env->get_temp_filepath("ParseInRangeIntegers.csv");
 
-  write_csv_helper(filepath, input_table, false);
+  write_csv_helper(filepath, input_table);
 
   cudf::io::csv_reader_options in_opts =
     cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath}).header(-1);
@@ -2123,7 +2107,7 @@ TEST_F(CsvReaderTest, ParseOutOfRangeIntegers)
 
   auto filepath = temp_env->get_temp_filepath("ParseOutOfRangeIntegers.csv");
 
-  write_csv_helper(filepath, input_table, false);
+  write_csv_helper(filepath, input_table);
 
   cudf::io::csv_reader_options in_opts =
     cudf::io::csv_reader_options::builder(cudf::io::source_info{filepath}).header(-1);