Centralize chunked reading code in the parquet reader to reader_impl_…

…chunking.cu (#14262)

As a precursor to further chunked reader work, this PR centralizes chunk-related code (mostly from the `reader::impl` class) into `reader_impl_chunking.cu` and `reader_impl_chunking.hpp`.  Also cleans up some variable naming and locations in `reader::impl` and the `file_intermediate_data` and `pass_intermediate_data classes`.

Authors:
  - https://github.com/nvdbaranec

Approvers:
  - Vukasin Milovanovic (https://github.com/vuule)
  - Robert Maynard (https://github.com/robertmaynard)
  - Nghia Truong (https://github.com/ttnghia)

URL: #14262

cpp/CMakeLists.txt

@@ -401,6 +401,7 @@ add_library(
   src/io/parquet/predicate_pushdown.cpp
   src/io/parquet/reader.cpp
   src/io/parquet/reader_impl.cpp
+  src/io/parquet/reader_impl_chunking.cu
   src/io/parquet/reader_impl_helpers.cpp
   src/io/parquet/reader_impl_preprocess.cu
   src/io/parquet/writer_impl.cu

cpp/src/io/parquet/parquet_gpu.hpp

@@ -318,79 +318,6 @@ struct ColumnChunkDesc {
   int32_t src_col_schema{};  // my schema index in the file
 };
 
-/**
- * @brief The row_group_info class
- */
-struct row_group_info {
-  size_type index;  // row group index within a file. aggregate_reader_metadata::get_row_group() is
-                    // called with index and source_index
-  size_t start_row;
-  size_type source_index;  // file index.
-
-  row_group_info() = default;
-
-  row_group_info(size_type index, size_t start_row, size_type source_index)
-    : index{index}, start_row{start_row}, source_index{source_index}
-  {
-  }
-};
-
-/**
- * @brief Struct to store file-level data that remains constant for
- * all passes/chunks for the file.
- */
-struct file_intermediate_data {
-  // all row groups to read
-  std::vector<row_group_info> row_groups{};
-
-  // all chunks from the selected row groups. We may end up reading these chunks progressively
-  // instead of all at once
-  std::vector<ColumnChunkDesc> chunks{};
-
-  // skip_rows/num_rows values for the entire file. these need to be adjusted per-pass because we
-  // may not be visiting every row group that contains these bounds
-  size_t global_skip_rows;
-  size_t global_num_rows;
-};
-
-/**
- * @brief Structs to identify the reading row range for each chunk of rows in chunked reading.
- */
-struct chunk_read_info {
-  size_t skip_rows;
-  size_t num_rows;
-};
-
-/**
- * @brief Struct to store pass-level data that remains constant for a single pass.
- */
-struct pass_intermediate_data {
-  std::vector<std::unique_ptr<datasource::buffer>> raw_page_data;
-  rmm::device_buffer decomp_page_data;
-
-  // rowgroup, chunk and page information for the current pass.
-  std::vector<row_group_info> row_groups{};
-  cudf::detail::hostdevice_vector<ColumnChunkDesc> chunks{};
-  cudf::detail::hostdevice_vector<PageInfo> pages_info{};
-  cudf::detail::hostdevice_vector<PageNestingInfo> page_nesting_info{};
-  cudf::detail::hostdevice_vector<PageNestingDecodeInfo> page_nesting_decode_info{};
-
-  rmm::device_uvector<int32_t> page_keys{0, rmm::cuda_stream_default};
-  rmm::device_uvector<int32_t> page_index{0, rmm::cuda_stream_default};
-  rmm::device_uvector<string_index_pair> str_dict_index{0, rmm::cuda_stream_default};
-
-  std::vector<chunk_read_info> output_chunk_read_info;
-  std::size_t current_output_chunk{0};
-
-  rmm::device_buffer level_decode_data{};
-  int level_type_size{0};
-
-  // skip_rows and num_rows values for this particular pass. these may be adjusted values from the
-  // global values stored in file_intermediate_data.
-  size_t skip_rows;
-  size_t num_rows;
-};
-
 /**
  * @brief Struct describing an encoder column
  */

cpp/src/io/parquet/reader_impl.cpp

@@ -349,22 +349,22 @@ void reader::impl::prepare_data(int64_t skip_rows,
         not _input_columns.empty()) {
       // fills in chunk information without physically loading or decompressing
       // the associated data
-      load_global_chunk_info();
+      create_global_chunk_info();
 
       // compute schedule of input reads. Each rowgroup contains 1 chunk per column. For now
       // we will read an entire row group at a time. However, it is possible to do
       // sub-rowgroup reads if we made some estimates on individual chunk sizes (tricky) and
       // changed the high level structure such that we weren't always reading an entire table's
       // worth of columns at once.
-      compute_input_pass_row_group_info();
+      compute_input_passes();
     }
 
     _file_preprocessed = true;
   }
 
   // if we have to start a new pass, do that now
   if (!_pass_preprocessed) {
-    auto const num_passes = _input_pass_row_group_offsets.size() - 1;
+    auto const num_passes = _file_itm_data.input_pass_row_group_offsets.size() - 1;
 
     // always create the pass struct, even if we end up with no passes.
     // this will also cause the previous pass information to be deleted
@@ -373,7 +373,7 @@ void reader::impl::prepare_data(int64_t skip_rows,
     if (_file_itm_data.global_num_rows > 0 && not _file_itm_data.row_groups.empty() &&
         not _input_columns.empty() && _current_input_pass < num_passes) {
       // setup the pass_intermediate_info for this pass.
-      setup_pass();
+      setup_next_pass();
 
       load_and_decompress_data();
       preprocess_pages(uses_custom_row_bounds, _output_chunk_read_limit);
@@ -541,8 +541,8 @@ bool reader::impl::has_next()
                {} /*row_group_indices, empty means read all row groups*/,
                std::nullopt /*filter*/);
 
-  auto const num_input_passes =
-    _input_pass_row_group_offsets.size() == 0 ? 0 : _input_pass_row_group_offsets.size() - 1;
+  size_t const num_input_passes = std::max(
+    int64_t{0}, static_cast<int64_t>(_file_itm_data.input_pass_row_group_offsets.size()) - 1);
   return (_pass_itm_data->current_output_chunk < _pass_itm_data->output_chunk_read_info.size()) ||
          (_current_input_pass < num_input_passes);
 }

cpp/src/io/parquet/reader_impl.hpp

@@ -22,6 +22,7 @@
 #pragma once
 
 #include "parquet_gpu.hpp"
+#include "reader_impl_chunking.hpp"
 #include "reader_impl_helpers.hpp"
 
 #include <cudf/io/datasource.hpp>
@@ -136,10 +137,6 @@ class reader::impl {
                     host_span<std::vector<size_type> const> row_group_indices,
                     std::optional<std::reference_wrapper<ast::expression const>> filter);
 
-  void load_global_chunk_info();
-  void compute_input_pass_row_group_info();
-  void setup_pass();
-
   /**
    * @brief Create chunk information and start file reads
    *
@@ -250,6 +247,31 @@ class reader::impl {
    */
   void decode_page_data(size_t skip_rows, size_t num_rows);
 
+  /**
+   * @brief Creates file-wide parquet chunk information.
+   *
+   * Creates information about all chunks in the file, storing it in
+   * the file-wide _file_itm_data structure.
+   */
+  void create_global_chunk_info();
+
+  /**
+   * @brief Computes all of the passes we will perform over the file.
+   */
+  void compute_input_passes();
+
+  /**
+   * @brief Close out the existing pass (if any) and prepare for the next pass.
+   */
+  void setup_next_pass();
+
+  /**
+   * @brief Given a set of pages that have had their sizes computed by nesting level and
+   * a limit on total read size, generate a set of {skip_rows, num_rows} pairs representing
+   * a set of reads that will generate output columns of total size <= `chunk_read_limit` bytes.
+   */
+  void compute_splits_for_pass();
+
  private:
   rmm::cuda_stream_view _stream;
   rmm::mr::device_memory_resource* _mr = nullptr;
@@ -278,27 +300,24 @@ class reader::impl {
 
   // chunked reading happens in 2 parts:
   //
-  // At the top level there is the "pass" in which we try and limit the
+  // At the top level, the entire file is divided up into "passes" omn which we try and limit the
   // total amount of temporary memory (compressed data, decompressed data) in use
   // via _input_pass_read_limit.
   //
   // Within a pass, we produce one or more chunks of output, whose maximum total
   // byte size is controlled by _output_chunk_read_limit.
 
   file_intermediate_data _file_itm_data;
+  bool _file_preprocessed{false};
+
   std::unique_ptr<pass_intermediate_data> _pass_itm_data;
+  bool _pass_preprocessed{false};
 
-  // an array of offsets into _file_itm_data::global_chunks. Each pair of offsets represents
-  // the start/end of the chunks to be loaded for a given pass.
-  std::vector<std::size_t> _input_pass_row_group_offsets{};
-  std::vector<std::size_t> _input_pass_row_count{};
-  std::size_t _current_input_pass{0};
-  std::size_t _chunk_count{0};
+  std::size_t _output_chunk_read_limit{0};  // output chunk size limit in bytes
+  std::size_t _input_pass_read_limit{0};    // input pass memory usage limit in bytes
 
-  std::size_t _output_chunk_read_limit{0};
-  std::size_t _input_pass_read_limit{0};
-  bool _pass_preprocessed{false};
-  bool _file_preprocessed{false};
+  std::size_t _current_input_pass{0};  // current input pass index
+  std::size_t _chunk_count{0};         // how many output chunks we have produced
 };
 
 }  // namespace cudf::io::parquet::detail