table_view.hpp

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/*
 * SPDX-FileCopyrightText: Copyright (c) 2019-2024, NVIDIA CORPORATION.
 * SPDX-License-Identifier: Apache-2.0
 */
#pragma once
 
#include <cudf/column/column_view.hpp>
#include <cudf/types.hpp>
#include <cudf/utilities/export.hpp>
 
#include <algorithm>
#include <vector>
 
namespace CUDF_EXPORT cudf {
namespace detail {
template <typename ColumnView>
class table_view_base {
  static_assert(std::is_same_v<ColumnView, column_view> or
                  std::is_same_v<ColumnView, mutable_column_view>,
                "table_view_base can only be instantiated with column_view or "
                "column_view_base.");
 
 private:
  std::vector<ColumnView> _columns{};  
  size_type _num_rows{};               
 
 public:
  using iterator       = decltype(std::begin(_columns));   
  using const_iterator = decltype(std::cbegin(_columns));  
 
  explicit table_view_base(std::vector<ColumnView> const& cols);
 
  iterator begin() noexcept { return std::begin(_columns); }
 
  [[nodiscard]] const_iterator begin() const noexcept { return std::begin(_columns); }
 
  iterator end() noexcept { return std::end(_columns); }
 
  [[nodiscard]] const_iterator end() const noexcept { return std::end(_columns); }
 
  [[nodiscard]] ColumnView const& column(size_type column_index) const
  {
    return _columns.at(column_index);
  }
 
  [[nodiscard]] size_type num_columns() const noexcept { return _columns.size(); }
 
  [[nodiscard]] size_type num_rows() const noexcept { return _num_rows; }
 
  [[nodiscard]] size_type is_empty() const noexcept { return num_columns() == 0; }
 
  table_view_base() = default;
 
  ~table_view_base() = default;
 
  table_view_base(table_view_base const&) = default;  
 
  table_view_base(table_view_base&&) = default;  
  table_view_base& operator=(table_view_base const&) = default;
  table_view_base& operator=(table_view_base&&) = default;
};
 
bool has_nested_columns(table_view const& table);
 
}  // namespace detail
 
bool has_nested_columns(table_view const& table);
 
class table_view : public detail::table_view_base<column_view> {
  using detail::table_view_base<column_view>::table_view_base;
 
 public:
  using ColumnView = column_view;  
 
  table_view() = default;
 
  table_view(std::vector<table_view> const& views);
 
  template <typename InputIterator>
  [[nodiscard]] table_view select(InputIterator begin, InputIterator end) const
  {
    std::vector<column_view> columns(std::distance(begin, end));
    std::transform(begin, end, columns.begin(), [this](auto index) { return this->column(index); });
    return table_view{columns};
  }
 
  [[nodiscard]] table_view select(std::vector<size_type> const& column_indices) const;
};
 
class mutable_table_view : public detail::table_view_base<mutable_column_view> {
  using detail::table_view_base<mutable_column_view>::table_view_base;
 
 public:
  using ColumnView = mutable_column_view;  
 
  mutable_table_view() = default;
 
  [[nodiscard]] mutable_column_view& column(size_type column_index) const
  {
    return const_cast<mutable_column_view&>(table_view_base::column(column_index));
  }
  operator table_view();
 
  mutable_table_view(std::vector<mutable_table_view> const& views);
};
 
bool nullable(table_view const& view);
 
bool has_nulls(table_view const& view);
 
bool has_nested_nulls(table_view const& input);
 
bool has_nested_nullable_columns(table_view const& input);
 
std::vector<column_view> get_nullable_columns(table_view const& table);
 
table_view scatter_columns(table_view const& source,
                           std::vector<size_type> const& map,
                           table_view const& target);
 
namespace detail {
template <typename TableView>
bool is_relationally_comparable(TableView const& lhs, TableView const& rhs);
// @cond
extern template bool is_relationally_comparable<table_view>(table_view const& lhs,
                                                            table_view const& rhs);
extern template bool is_relationally_comparable<mutable_table_view>(mutable_table_view const& lhs,
                                                                    mutable_table_view const& rhs);
// @endcond
}  // namespace detail
}  // namespace CUDF_EXPORT cudf