Fix an issue with multiple short list rowgroups using the Parquet chunked reader.

cpp/src/io/parquet/reader_impl_chunking.cu

@@ -48,9 +48,9 @@ struct split_info {
 };
 
 struct cumulative_page_info {
-  size_t row_index;   // row index
-  size_t size_bytes;  // cumulative size in bytes
-  int key;            // schema index
+  size_t end_row_index;  // end row index (exclusive)
+  size_t size_bytes;     // cumulative size in bytes
+  int key;               // schema index
 };
 
 // the minimum amount of memory we can safely expect to be enough to
@@ -260,7 +260,7 @@ struct set_row_index {
     auto const& chunk         = chunks[page.chunk_idx];
     size_t const page_end_row = chunk.start_row + page.chunk_row + page.num_rows;
     // if we have been passed in a cap, apply it
-    c_info[i].row_index = max_row > 0 ? min(max_row, page_end_row) : page_end_row;
+    c_info[i].end_row_index = max_row > 0 ? min(max_row, page_end_row) : page_end_row;
   }
 };
 
@@ -293,13 +293,13 @@ struct page_total_size {
       auto const end   = key_offsets[idx + 1];
       auto iter        = cudf::detail::make_counting_transform_iterator(
         0, cuda::proclaim_return_type<size_t>([&] __device__(size_type i) {
-          return c_info[i].row_index;
+          return c_info[i].end_row_index;
         }));
       auto const page_index =
-        thrust::lower_bound(thrust::seq, iter + start, iter + end, i.row_index) - iter;
+        thrust::lower_bound(thrust::seq, iter + start, iter + end, i.end_row_index) - iter;
       sum += c_info[page_index].size_bytes;
     }
-    return {i.row_index, sum, i.key};
+    return {i.end_row_index, sum, i.key};
   }
 };
 
@@ -318,14 +318,15 @@ size_t find_start_index(cudf::host_span<cumulative_page_info const> aggregated_i
                         size_t start_row)
 {
   auto start = thrust::make_transform_iterator(
-    aggregated_info.begin(), [&](cumulative_page_info const& i) { return i.row_index; });
+    aggregated_info.begin(), [&](cumulative_page_info const& i) { return i.end_row_index; });
   auto start_index =
     thrust::lower_bound(thrust::host, start, start + aggregated_info.size(), start_row) - start;
 
-  // cumulative_page_info.row_index is the -end- of the rows of a given page. so move forward until
-  // we find the next group of pages
-  while (start_index < (static_cast<int64_t>(aggregated_info.size()) - 1) &&
-         (start_index < 0 || aggregated_info[start_index].row_index == start_row)) {
+  // list rows can span page boundaries, so it is not always safe to assume that the row
+  // represented by end_row_index starts on the subsequent page. It is possible that
+  // the values for row end_row_index start within the page itself. so we must
+  // include the page in that case.
+  while (start_index < (static_cast<int64_t>(aggregated_info.size()) - 1) && (start_index < 0)) {
     start_index++;
   }
 
@@ -353,16 +354,18 @@ int64_t find_next_split(int64_t cur_pos,
   int64_t split_pos = thrust::lower_bound(thrust::seq, start + cur_pos, end, size_limit) - start;
 
   // if we're past the end, or if the returned bucket is > than the chunk_read_limit, move back
-  // one.
+  // one. note that in the case where we can't even fit the current set of rows within the size
+  // limit, this will cause split_pos to go below cur_pos.  but that is handled in the loop below.
   if (static_cast<size_t>(split_pos) >= sizes.size() ||
       (sizes[split_pos].size_bytes - cur_cumulative_size > size_limit)) {
     split_pos--;
   }
 
-  // cumulative_page_info.row_index is the -end- of the rows of a given page. so move forward until
-  // we find the next group of pages
+  // move forward until we find the next group of pages that will actually advance our row count.
+  // this guarantees that even if we cannot fit the set of rows represented by our where our cur_pos
+  // is, we will still move forward instead of failing.
   while (split_pos < (static_cast<int64_t>(sizes.size()) - 1) &&
-         (split_pos < 0 || sizes[split_pos].row_index == cur_row_index)) {
+         (split_pos < cur_pos || sizes[split_pos].end_row_index == cur_row_index)) {
     split_pos++;
   }
 
@@ -413,7 +416,7 @@ template <typename T = uint8_t>
 struct row_count_less {
   __device__ bool operator()(cumulative_page_info const& a, cumulative_page_info const& b) const
   {
-    return a.row_index < b.row_index;
+    return a.end_row_index < b.end_row_index;
   }
 };
 
@@ -501,10 +504,10 @@ struct page_span {
   size_t start, end;
 };
 
-struct get_page_row_index {
+struct get_page_end_row_index {
   device_span<cumulative_page_info const> c_info;
 
-  __device__ size_t operator()(size_t i) const { return c_info[i].row_index; }
+  __device__ size_t operator()(size_t i) const { return c_info[i].end_row_index; }
 };
 
 /**
@@ -514,15 +517,18 @@ struct get_page_row_index {
 template <typename RowIndexIter>
 struct get_page_span {
   device_span<size_type const> page_offsets;
+  device_span<ColumnChunkDesc const> chunks;
   RowIndexIter page_row_index;
   size_t const start_row;
   size_t const end_row;
 
   get_page_span(device_span<size_type const> _page_offsets,
+                device_span<ColumnChunkDesc const> _chunks,
                 RowIndexIter _page_row_index,
                 size_t _start_row,
                 size_t _end_row)
     : page_offsets(_page_offsets),
+      chunks(_chunks),
       page_row_index(_page_row_index),
       start_row(_start_row),
       end_row(_end_row)
@@ -535,12 +541,17 @@ struct get_page_span {
     auto const column_page_start = page_row_index + first_page_index;
     auto const column_page_end   = page_row_index + page_offsets[column_index + 1];
     auto const num_pages         = column_page_end - column_page_start;
+    bool const is_list           = chunks[column_index].max_level[level_type::REPETITION] > 0;
 
     auto start_page =
       (thrust::lower_bound(thrust::seq, column_page_start, column_page_end, start_row) -
        column_page_start) +
       first_page_index;
-    if (page_row_index[start_page] == start_row) { start_page++; }
+    // list rows can span page boundaries, so it is not always safe to assume that the row
+    // represented by end_row_index starts on the subsequent page. It is possible that
+    // the values for row end_row_index start within the page itself. so we must
+    // include the page in that case.
+    if (page_row_index[start_page] == start_row && !is_list) { start_page++; }
 
     auto end_page = (thrust::lower_bound(thrust::seq, column_page_start, column_page_end, end_row) -
                      column_page_start) +
@@ -623,6 +634,7 @@ struct copy_subpass_page {
  *
  * @param c_info The cumulative page size information (row count and byte size) per column
  * @param pages All of the pages in the pass
+ * @param chunks All of the chunks in the pass
  * @param page_offsets Offsets into the pages array representing the first page for each column
  * @param start_row The row to start the subpass at
  * @param size_limit The size limit in bytes of the subpass
@@ -636,6 +648,7 @@ struct copy_subpass_page {
 std::tuple<rmm::device_uvector<page_span>, size_t, size_t> compute_next_subpass(
   device_span<cumulative_page_info const> c_info,
   device_span<PageInfo const> pages,
+  device_span<ColumnChunkDesc const> chunks,
   device_span<size_type const> page_offsets,
   size_t start_row,
   size_t size_limit,
@@ -658,18 +671,18 @@ std::tuple<rmm::device_uvector<page_span>, size_t, size_t> compute_next_subpass(
     start_row == 0 || start_index == 0 ? 0 : h_aggregated_info[start_index - 1].size_bytes;
   auto const end_index =
     find_next_split(start_index, start_row, cumulative_size, h_aggregated_info, size_limit);
-  auto const end_row = h_aggregated_info[end_index].row_index;
+  auto const end_row = h_aggregated_info[end_index].end_row_index;
 
   // for each column, collect the set of pages that spans start_row / end_row
   rmm::device_uvector<page_span> page_bounds(num_columns, stream);
   auto iter = thrust::make_counting_iterator(size_t{0});
   auto page_row_index =
-    cudf::detail::make_counting_transform_iterator(0, get_page_row_index{c_info});
+    cudf::detail::make_counting_transform_iterator(0, get_page_end_row_index{c_info});
   thrust::transform(rmm::exec_policy_nosync(stream),
                     iter,
                     iter + num_columns,
                     page_bounds.begin(),
-                    get_page_span{page_offsets, page_row_index, start_row, end_row});
+                    get_page_span{page_offsets, chunks, page_row_index, start_row, end_row});
 
   // total page count over all columns
   auto page_count_iter = thrust::make_transform_iterator(page_bounds.begin(), get_span_size{});
@@ -700,13 +713,13 @@ std::vector<row_range> compute_page_splits_by_row(device_span<cumulative_page_in
   size_t cur_pos             = find_start_index(h_aggregated_info, skip_rows);
   size_t cur_row_index       = skip_rows;
   size_t cur_cumulative_size = 0;
-  auto const max_row         = min(skip_rows + num_rows, h_aggregated_info.back().row_index);
+  auto const max_row         = min(skip_rows + num_rows, h_aggregated_info.back().end_row_index);
   while (cur_row_index < max_row) {
     auto const split_pos =
       find_next_split(cur_pos, cur_row_index, cur_cumulative_size, h_aggregated_info, size_limit);
 
     auto const start_row = cur_row_index;
-    cur_row_index        = min(max_row, h_aggregated_info[split_pos].row_index);
+    cur_row_index        = min(max_row, h_aggregated_info[split_pos].end_row_index);
     splits.push_back({start_row, cur_row_index - start_row});
     cur_pos             = split_pos;
     cur_cumulative_size = h_aggregated_info[split_pos].size_bytes;
@@ -1375,6 +1388,7 @@ void reader::impl::setup_next_subpass(bool uses_custom_row_bounds)
     // get the next batch of pages
     return compute_next_subpass(c_info,
                                 pass.pages,
+                                pass.chunks,
                                 pass.page_offsets,
                                 pass.processed_rows + pass.skip_rows,
                                 remaining_read_limit,

cpp/src/io/parquet/reader_impl_preprocess.cu

@@ -700,16 +700,16 @@ struct set_list_row_count_estimate {
 struct set_final_row_count {
   device_span<PageInfo> pages;
   device_span<const ColumnChunkDesc> chunks;
-  device_span<const size_type> page_offsets;
-  size_t const max_row;
 
   __device__ void operator()(size_t i)
   {
-    auto const last_page_index      = page_offsets[i + 1] - 1;
-    auto const& page                = pages[last_page_index];
-    auto const& chunk               = chunks[page.chunk_idx];
-    size_t const page_start_row     = chunk.start_row + page.chunk_row;
-    pages[last_page_index].num_rows = max_row - page_start_row;
+    auto& page        = pages[i];
+    auto const& chunk = chunks[page.chunk_idx];
+    // only do this for the last page in each chunk
+    if (i < pages.size() && (pages[i + 1].chunk_idx == page.chunk_idx)) { return; }
+    size_t const page_start_row = chunk.start_row + page.chunk_row;
+    size_t const chunk_last_row = chunk.start_row + chunk.num_rows;
+    page.num_rows               = chunk_last_row - page_start_row;
   }
 };
 
@@ -1300,17 +1300,15 @@ void reader::impl::generate_list_column_row_count_estimates()
                                   chunk_row_output_iter{pass.pages.device_ptr()});
   }
 
-  // finally, fudge the last page for each column such that it ends on the real known row count
-  // for the pass. this is so that as we march through the subpasses, we will find that every column
-  // cleanly ends up the expected row count at the row group boundary.
-  auto const& last_chunk = pass.chunks[pass.chunks.size() - 1];
-  auto const num_columns = _input_columns.size();
-  size_t const max_row   = last_chunk.start_row + last_chunk.num_rows;
-  auto iter              = thrust::make_counting_iterator(0);
+  // to compensate for the list row size estimates, force the row count on the last page for each
+  // column chunk (each rowgroup) such that it ends on the real known row count. this is so that as
+  // we march through the subpasses, we will find that every column cleanly ends up the expected row
+  // count at the row group boundary and our split computations work correctly.
+  auto iter = thrust::make_counting_iterator(0);
   thrust::for_each(rmm::exec_policy_nosync(_stream),
                    iter,
-                   iter + num_columns,
-                   set_final_row_count{pass.pages, pass.chunks, pass.page_offsets, max_row});
+                   iter + pass.pages.size(),
+                   set_final_row_count{pass.pages, pass.chunks});
 
   pass.chunks.device_to_host_async(_stream);
   pass.pages.device_to_host_async(_stream);

cpp/tests/io/parquet_chunked_reader_test.cu

@@ -111,12 +111,12 @@ auto write_file(std::vector<std::unique_ptr<cudf::column>>& input_columns,
   return std::pair{std::move(input_table), std::move(filepath)};
 }
 
-auto chunked_read(std::string const& filepath,
+auto chunked_read(std::vector<std::string> const& filepaths,
                   std::size_t output_limit,
                   std::size_t input_limit = 0)
 {
   auto const read_opts =
-    cudf::io::parquet_reader_options::builder(cudf::io::source_info{filepath}).build();
+    cudf::io::parquet_reader_options::builder(cudf::io::source_info{filepaths}).build();
   auto reader = cudf::io::chunked_parquet_reader(output_limit, input_limit, read_opts);
 
   auto num_chunks = 0;
@@ -141,6 +141,14 @@ auto chunked_read(std::string const& filepath,
   return std::pair(cudf::concatenate(out_tviews), num_chunks);
 }
 
+auto chunked_read(std::string const& filepath,
+                  std::size_t output_limit,
+                  std::size_t input_limit = 0)
+{
+  std::vector<std::string> vpath{filepath};
+  return chunked_read(vpath, output_limit, input_limit);
+}
+
 }  // namespace
 
 struct ParquetChunkedReaderTest : public cudf::test::BaseFixture {};
@@ -1113,7 +1121,7 @@ TEST_F(ParquetChunkedReaderInputLimitConstrainedTest, SingleFixedWidthColumn)
   input_limit_test_write(test_filenames, tbl);
 
   // semi-reasonable limit
-  constexpr int expected_a[] = {1, 17, 4, 1};
+  constexpr int expected_a[] = {1, 25, 5, 1};
   input_limit_test_read(test_filenames, tbl, 0, 2 * 1024 * 1024, expected_a);
   // an unreasonable limit
   constexpr int expected_b[] = {1, 50, 50, 1};
@@ -1145,7 +1153,7 @@ TEST_F(ParquetChunkedReaderInputLimitConstrainedTest, MixedColumns)
 
   input_limit_test_write(test_filenames, tbl);
 
-  constexpr int expected_a[] = {1, 50, 10, 7};
+  constexpr int expected_a[] = {1, 50, 13, 7};
   input_limit_test_read(test_filenames, tbl, 0, 2 * 1024 * 1024, expected_a);
   constexpr int expected_b[] = {1, 50, 50, 50};
   input_limit_test_read(test_filenames, tbl, 0, 1, expected_b);
@@ -1227,6 +1235,76 @@ TEST_F(ParquetChunkedReaderInputLimitTest, List)
   input_limit_test_read(test_filenames, tbl, 128 * 1024 * 1024, 512 * 1024 * 1024, expected_c);
 }
 
+void tiny_list_rowgroup_test(bool just_list_col)
+{
+  auto iter = thrust::make_counting_iterator(0);
+
+  // test a specific edge case:  a list column composed of multiple row groups, where each row
+  // group contains a single, relatively small row.
+  std::vector<int> row_sizes{12, 7, 16, 20, 10, 3, 15};
+  std::vector<std::unique_ptr<cudf::table>> row_groups;
+  for (size_t idx = 0; idx < row_sizes.size(); idx++) {
+    std::vector<std::unique_ptr<cudf::column>> cols;
+
+    // add a column before the list
+    if (!just_list_col) {
+      cudf::test::fixed_width_column_wrapper<int> int_col({idx});
+      cols.push_back(int_col.release());
+    }
+
+    // write out the single-row list column as it's own file
+    cudf::test::fixed_width_column_wrapper<int> values(iter, iter + row_sizes[idx]);
+    cudf::test::fixed_width_column_wrapper<int> offsets({0, row_sizes[idx]});
+    cols.push_back(cudf::make_lists_column(1, offsets.release(), values.release(), 0, {}));
+
+    // add a column after the list
+    if (!just_list_col) {
+      cudf::test::fixed_width_column_wrapper<float> float_col({idx});
+      cols.push_back(float_col.release());
+    }
+
+    auto tbl = std::make_unique<cudf::table>(std::move(cols));
+
+    auto filepath = temp_env->get_temp_filepath("Tlrg" + std::to_string(idx));
+    auto const write_opts =
+      cudf::io::parquet_writer_options::builder(cudf::io::sink_info{filepath}, *tbl).build();
+    cudf::io::write_parquet(write_opts);
+
+    // store off the table
+    row_groups.push_back(std::move(tbl));
+  }
+
+  // build expected
+  std::vector<cudf::table_view> views;
+  std::transform(row_groups.begin(),
+                 row_groups.end(),
+                 std::back_inserter(views),
+                 [](std::unique_ptr<cudf::table> const& tbl) { return tbl->view(); });
+  auto expected = cudf::concatenate(views);
+
+  // load the individual files all at once
+  std::vector<std::string> source_files;
+  std::transform(iter, iter + row_groups.size(), std::back_inserter(source_files), [](int i) {
+    return temp_env->get_temp_filepath("Tlrg" + std::to_string(i));
+  });
+  auto result =
+    chunked_read(source_files, size_t{2} * 1024 * 1024 * 1024, size_t{2} * 1024 * 1024 * 1024);
+
+  CUDF_TEST_EXPECT_TABLES_EQUAL(*expected, *(result.first));
+}
+
+TEST_F(ParquetChunkedReaderInputLimitTest, TinyListRowGroupsSingle)
+{
+  // test with just a single list column
+  tiny_list_rowgroup_test(true);
+}
+
+TEST_F(ParquetChunkedReaderInputLimitTest, TinyListRowGroupsMixed)
+{
+  // test with other columns mixed in
+  tiny_list_rowgroup_test(false);
+}
+
 struct char_values {
   __device__ int8_t operator()(int i)
   {