Bind read_parquet_metadata API to libcudf instead of pyarrow and extract RowGroup information

cpp/include/cudf/io/parquet_metadata.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, NVIDIA CORPORATION.
+ * Copyright (c) 2023-2024, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -59,6 +59,13 @@ enum class TypeKind : int8_t {
  */
 struct parquet_column_schema {
  public:
+  /**
+   * @brief Default constructor.
+   *
+   * This has been added since Cython requires a default constructor to create objects on stack.
+   */
+  explicit parquet_column_schema() = default;
+
   /**
    * @brief constructor
    *
@@ -134,6 +141,13 @@ struct parquet_column_schema {
  */
 struct parquet_schema {
  public:
+  /**
+   * @brief Default constructor.
+   *
+   * This has been added since Cython requires a default constructor to create objects on stack.
+   */
+  explicit parquet_schema() = default;
+
   /**
    * @brief constructor
    *
@@ -165,6 +179,15 @@ class parquet_metadata {
  public:
   /// Key-value metadata in the file footer.
   using key_value_metadata = std::unordered_map<std::string, std::string>;
+  /// row group metadata from each RowGroup element.
+  using row_group_metadata = std::unordered_map<std::string, int64_t>;
+
+  /**
+   * @brief Default constructor.
+   *
+   * This has been added since Cython requires a default constructor to create objects on stack.
+   */
+  explicit parquet_metadata() = default;
 
   /**
    * @brief constructor
@@ -173,15 +196,18 @@ class parquet_metadata {
    * @param num_rows number of rows
    * @param num_rowgroups number of row groups
    * @param file_metadata key-value metadata in the file footer
+   * @param rg_metadata vector of maps containing metadata for each row group
    */
   parquet_metadata(parquet_schema schema,
                    int64_t num_rows,
                    size_type num_rowgroups,
-                   key_value_metadata file_metadata)
+                   key_value_metadata file_metadata,
+                   std::vector<row_group_metadata> rg_metadata)
     : _schema{std::move(schema)},
       _num_rows{num_rows},
       _num_rowgroups{num_rowgroups},
-      _file_metadata{std::move(file_metadata)}
+      _file_metadata{std::move(file_metadata)},
+      _rowgroup_metadata{std::move(rg_metadata)}
   {
   }
 
@@ -207,18 +233,27 @@ class parquet_metadata {
    * @return Number of row groups
    */
   [[nodiscard]] auto num_rowgroups() const { return _num_rowgroups; }
+
   /**
    * @brief Returns the Key value metadata in the file footer.
    *
    * @return Key value metadata as a map
    */
   [[nodiscard]] auto const& metadata() const { return _file_metadata; }
 
+  /**
+   * @brief Returns the row group metadata in the file footer.
+   *
+   * @return vector of row group metadata as maps
+   */
+  [[nodiscard]] auto const& rowgroup_metadata() const { return _rowgroup_metadata; }
+
  private:
   parquet_schema _schema;
   int64_t _num_rows;
   size_type _num_rowgroups;
   key_value_metadata _file_metadata;
+  std::vector<row_group_metadata> _rowgroup_metadata;
 };
 
 /**

cpp/src/io/parquet/reader_impl.cpp

@@ -607,7 +607,8 @@ parquet_metadata read_parquet_metadata(host_span<std::unique_ptr<datasource> con
   return parquet_metadata{parquet_schema{walk_schema(&metadata, 0)},
                           metadata.get_num_rows(),
                           metadata.get_num_row_groups(),
-                          metadata.get_key_value_metadata()[0]};
+                          metadata.get_key_value_metadata()[0],
+                          metadata.get_rowgroup_metadata()};
 }
 
 }  // namespace cudf::io::parquet::detail

cpp/src/io/parquet/reader_impl_helpers.cpp

@@ -560,6 +560,26 @@ ColumnChunkMetaData const& aggregate_reader_metadata::get_column_metadata(size_t
   return col->meta_data;
 }
 
+std::vector<std::unordered_map<std::string, int64_t>>
+aggregate_reader_metadata::get_rowgroup_metadata() const
+{
+  std::vector<std::unordered_map<std::string, int64_t>> rg_metadata;
+
+  std::for_each(
+    per_file_metadata.cbegin(), per_file_metadata.cend(), [&rg_metadata](auto const& pfm) {
+      std::transform(pfm.row_groups.cbegin(),
+                     pfm.row_groups.cend(),
+                     std::back_inserter(rg_metadata),
+                     [](auto const& rg) {
+                       std::unordered_map<std::string, int64_t> rg_meta_map;
+                       rg_meta_map["num_rows"]        = rg.num_rows;
+                       rg_meta_map["total_byte_size"] = rg.total_byte_size;
+                       return rg_meta_map;
+                     });
+    });
+  return rg_metadata;
+}
+
 std::string aggregate_reader_metadata::get_pandas_index() const
 {
   // Assumes that all input files have the same metadata

cpp/src/io/parquet/reader_impl_helpers.hpp

@@ -166,6 +166,13 @@ class aggregate_reader_metadata {
                                                                size_type src_idx,
                                                                int schema_idx) const;
 
+  /**
+   * @brief Extracts high-level metadata for all row groups
+   *
+   * @return List of maps containing metadata information for each row group
+   */
+  [[nodiscard]] std::vector<std::unordered_map<std::string, int64_t>> get_rowgroup_metadata() const;
+
   [[nodiscard]] auto get_num_rows() const { return num_rows; }
 
   [[nodiscard]] auto get_num_row_groups() const { return num_row_groups; }
@@ -178,6 +185,7 @@ class aggregate_reader_metadata {
   [[nodiscard]] auto const& get_key_value_metadata() const& { return keyval_maps; }
 
   [[nodiscard]] auto&& get_key_value_metadata() && { return std::move(keyval_maps); }
+
   /**
    * @brief Gets the concrete nesting depth of output cudf columns
    *

python/cudf/cudf/_lib/cpp/io/parquet_metadata.pxd

@@ -0,0 +1,32 @@
+# Copyright (c) 2024, NVIDIA CORPORATION.
+
+from libc.stdint cimport int64_t
+from libcpp.string cimport string
+from libcpp.unordered_map cimport unordered_map
+from libcpp.vector cimport vector
+
+cimport cudf._lib.cpp.io.types as cudf_io_types
+from cudf._lib.cpp.types cimport size_type
+
+
+cdef extern from "cudf/io/parquet_metadata.hpp" namespace "cudf::io" nogil:
+    cdef cppclass parquet_column_schema:
+        parquet_column_schema() except+
+        string name() except+
+        size_type num_children() except+
+        parquet_column_schema child(int idx) except+
+        vector[parquet_column_schema] children() except+
+
+    cdef cppclass parquet_schema:
+        parquet_schema() except+
+        parquet_column_schema root() except+
+
+    cdef cppclass parquet_metadata:
+        parquet_metadata() except+
+        parquet_schema schema() except+
+        int64_t num_rows() except+
+        size_type num_rowgroups() except+
+        unordered_map[string, string] metadata() except+
+        vector[unordered_map[string, int64_t]] rowgroup_metadata() except+
+
+    cdef parquet_metadata read_parquet_metadata(cudf_io_types.source_info src) except+

python/cudf/cudf/_lib/parquet.pyx

@@ -46,6 +46,10 @@ from cudf._lib.cpp.io.parquet cimport (
     read_parquet as parquet_reader,
     write_parquet as parquet_writer,
 )
+from cudf._lib.cpp.io.parquet_metadata cimport (
+    parquet_metadata,
+    read_parquet_metadata as parquet_metadata_reader,
+)
 from cudf._lib.cpp.io.types cimport column_in_metadata, table_input_metadata
 from cudf._lib.cpp.table.table_view cimport table_view
 from cudf._lib.cpp.types cimport data_type, size_type
@@ -316,6 +320,71 @@ cpdef read_parquet(filepaths_or_buffers, columns=None, row_groups=None,
         df._data.label_dtype = cudf.dtype(column_index_type)
     return df
 
+cpdef read_parquet_metadata(filepaths_or_buffers):
+    """
+    Cython function to call into libcudf API, see `read_parquet_metadata`.
+
+    See Also
+    --------
+    cudf.io.parquet.read_parquet
+    cudf.io.parquet.to_parquet
+    """
+    # Convert NativeFile buffers to NativeFileDatasource
+    for i, datasource in enumerate(filepaths_or_buffers):
+        if isinstance(datasource, NativeFile):
+            filepaths_or_buffers[i] = NativeFileDatasource(datasource)
+
+    cdef cudf_io_types.source_info source = make_source_info(filepaths_or_buffers)
+
+    args = move(source)
+
+    cdef parquet_metadata c_result
+
+    # Read Parquet metadata
+    with nogil:
+        c_result = move(parquet_metadata_reader(args))
+
+    # access and return results
+    num_rows = c_result.num_rows()
+    num_rowgroups = c_result.num_rowgroups()
+
+    # extract row group metadata and sanitize keys
+    row_group_metadata = [{k.decode(): v for k, v in metadata}
+                          for metadata in c_result.rowgroup_metadata()]
+
+    # read all column names including index column, if any
+    col_names = [info.name().decode() for info in c_result.schema().root().children()]
+
+    # access the Parquet file_footer to find the index
+    index_col = None
+    cdef unordered_map[string, string] file_footer = c_result.metadata()
+
+    # get index column name(s)
+    index_col_names = None
+    json_str = file_footer[b'pandas'].decode('utf-8')
+    meta = None
+    if json_str != "":
+        meta = json.loads(json_str)
+        file_is_range_index, index_col, _ = _parse_metadata(meta)
+        if not file_is_range_index and index_col is not None \
+                and index_col_names is None:
+            index_col_names = {}
+            for idx_col in index_col:
+                for c in meta['columns']:
+                    if c['field_name'] == idx_col:
+                        index_col_names[idx_col] = c['name']
+
+    # remove the index column from the list of column names
+    # only if index_col_names is not None
+    if index_col_names is not None:
+        col_names = [name for name in col_names if name not in index_col_names]
+
+    # num_columns = length of list(col_names)
+    num_columns = len(col_names)
+
+    # return the metadata
+    return num_rows, num_rowgroups, col_names, num_columns, row_group_metadata
+
 
 @acquire_spill_lock()
 def write_parquet(

python/cudf/cudf/io/parquet.py

@@ -267,17 +267,45 @@ def write_to_dataset(
 
 @ioutils.doc_read_parquet_metadata()
 @_cudf_nvtx_annotate
-def read_parquet_metadata(path):
+def read_parquet_metadata(filepath_or_buffer):
     """{docstring}"""
-    import pyarrow.parquet as pq
+    # Multiple sources are passed as a list. If a single source is passed,
+    # wrap it in a list for unified processing downstream.
+    if not is_list_like(filepath_or_buffer):
+        filepath_or_buffer = [filepath_or_buffer]
 
-    pq_file = pq.ParquetFile(path)
+    # Start by trying to construct a filesystem object
+    fs, paths = ioutils._get_filesystem_and_paths(
+        path_or_data=filepath_or_buffer, storage_options=None
+    )
 
-    num_rows = pq_file.metadata.num_rows
-    num_row_groups = pq_file.num_row_groups
-    col_names = pq_file.schema.names
+    # Check if filepath or buffer
+    filepath_or_buffer = paths if paths else filepath_or_buffer
+
+    # List of filepaths or buffers
+    filepaths_or_buffers = []
+
+    for source in filepath_or_buffer:
+        tmp_source, compression = ioutils.get_reader_filepath_or_buffer(
+            path_or_data=source,
+            compression=None,
+            fs=fs,
+            use_python_file_object=True,
+            open_file_options=None,
+            storage_options=None,
+            bytes_per_thread=None,
+        )
+
+        if compression is not None:
+            raise ValueError(
+                "URL content-encoding decompression is not supported"
+            )
+        if isinstance(tmp_source, list):
+            filepath_or_buffer.extend(tmp_source)
+        else:
+            filepaths_or_buffers.append(tmp_source)
 
-    return num_rows, num_row_groups, col_names
+    return libparquet.read_parquet_metadata(filepaths_or_buffers)
 
 
 @_cudf_nvtx_annotate