Tables

Refer to Developer Guide: Tables.

Programming interface

All types and functions in this section are declared in the oneapi::dal namespace and be available via inclusion of the oneapi/dal/table/common.hpp header file.

Table

A base implementation of the table concept. The table type and all of its subtypes are reference-counted:

  1. The instance stores a pointer to table implementation that holds all property values and data

  2. The reference count indicating how many table objects refer to the same implementation.

  3. The table increments the reference count for it to be equal to the number of table objects sharing the same implementation.

  4. The table decrements the reference count when the table goes out of the scope. If the reference count is zero, the table frees its implementation.

class table

Constructors

table()

An empty table constructor: creates the table instance with zero number of rows and columns.

table(const table&) = default

Creates a new table instance that shares the implementation with another one.

table(table&&)

Creates a new table instance and moves implementation from another one into it.

Public Methods

table &operator=(const table&) = default

Replaces the implementation by another one.

table &operator=(table&&)

Swaps the implementation of this object and another one.

bool has_data() const noexcept

Indicates whether a table contains non-zero number of rows and columns.

std::int64_t get_column_count() const

The number of columns in the table.

std::int64_t get_row_count() const

The number of rows in the table.

const table_metadata &get_metadata() const

The metadata object that holds additional information about the data within the table.

std::int64_t get_kind() const

The runtime id of the table type. Each table sub-type has its unique kind. An empty table has a unique kind value as well.

data_layout get_data_layout() const

The layout of the data within the table.

Table metadata

An implementation of the table metadata concept. Holds additional information about data within the table. The objects of table_metadata are reference-counted.

class table_metadata

Constructors

table_metadata()

Creates the metadata instance without information about the features. The feature_count should be set to zero. The data_type and feature_type properties should not be initialized.

table_metadata(const array<data_type> &dtypes, const array<feature_type> &ftypes)

Creates the metadata instance from external information about the data types and the feature types.

Parameters
  • dtypes – The data types of the features. Assigned into the data_type property.

  • ftypes – The feature types. Assigned into the feature_type property.

Preconditions
dtypes.get_count() == ftypes.get_count()

Public Methods

std::int64_t get_feature_count() const

The number of features that metadata contains information about.

const feature_type &get_feature_type(std::int64_t feature_index) const

Feature types in the metadata object. Should be within the range [0, feature_count).

const data_type &get_data_type(std::int64_t feature_index) const

Data types of the features in the metadata object. Should be within the range [0, feature_count).

Data layout

An implementation of the data layout concept.

enum class data_layout { unknown, row_major, column_major };
data_layout::unknown

Represents the data layout that is undefined or unknown at this moment.

data_layout::row_major

The data block elements are stored in raw-major layout.

data_layout::column_major

The data block elements are stored in column_major layout.

Feature type

An implementation of the logical data types.

enum class feature_type { nominal, ordinal, interval, ratio };
feature_type::nominal

Represents the type of Nominal feature.

feature_type::ordinal

Represents the type of Ordinal feature.

feature_type::interval

Represents the type of Interval feature.

feature_type::ratio

Represents the type of Ratio feature.