A non-owning, immutable view of device data as a column of elements, some of which may be null as indicated by a bitmask. More...

#include <column_view.hpp>

Inheritance diagram for cudf::column_view:

Public Member Functions
	column_view (column_view const &)=default
	Copy constructor.

	column_view (column_view &&)=default
	Move constructor.

column_view &	operator= (column_view const &)=default
	Copy assignment operator. More...

column_view &	operator= (column_view &&)=default
	Move assignment operator. More...

	column_view (data_type type, size_type size, void const data, bitmask_type const null_mask, size_type null_count, size_type offset=0, std::vector< column_view > const &children={})
	Construct a `column_view` from pointers to device memory for the elements and bitmask of the column. More...

column_view	child (size_type child_index) const noexcept
	Returns the specified child. More...

size_type	num_children () const noexcept
	Returns the number of child columns. More...

auto	child_begin () const noexcept
	Returns iterator to the beginning of the ordered sequence of child column-views. More...

auto	child_end () const noexcept
	Returns iterator to the end of the ordered sequence of child column-views. More...

template<typename T , CUDF_ENABLE_IF(cudf::is_numeric< T >() or cudf::is_chrono< T >()) >
	column_view (device_span< T const > data)
	Construct a column view from a device_span<T>. More...

template<typename T , CUDF_ENABLE_IF(cudf::is_numeric< T >() or cudf::is_chrono< T >()) >
	operator device_span< T const > () const
	Converts a column view into a device span. More...

Public Member Functions inherited from cudf::detail::column_view_base
template<typename T = void, CUDF_ENABLE_IF(std::is_same_v< T, void > or is_rep_layout_compatible< T >()) >
T const *	head () const noexcept
	Returns pointer to the base device memory allocation casted to the specified type. More...

template<typename T , CUDF_ENABLE_IF(is_rep_layout_compatible< T >()) >
T const *	data () const noexcept
	Returns the underlying data casted to the specified type, plus the offset. More...

template<typename T , CUDF_ENABLE_IF(is_rep_layout_compatible< T >()) >
T const *	begin () const noexcept
	Return first element (accounting for offset) after underlying data is casted to the specified type. More...

template<typename T , CUDF_ENABLE_IF(is_rep_layout_compatible< T >()) >
T const *	end () const noexcept
	Return one past the last element after underlying data is casted to the specified type. More...

size_type	size () const noexcept
	Returns the number of elements in the column. More...

bool	is_empty () const noexcept
	Returns true if `size()` returns zero, or false otherwise. More...

data_type	type () const noexcept
	Returns the element `data_type` More...

bool	nullable () const noexcept
	Indicates if the column can contain null elements, i.e., if it has an allocated bitmask. More...

size_type	null_count () const
	Returns the count of null elements. More...

size_type	null_count (size_type begin, size_type end) const
	Returns the count of null elements in the range [begin, end) More...

bool	has_nulls () const
	Indicates if the column contains null elements, i.e., `null_count() > 0` More...

bool	has_nulls (size_type begin, size_type end) const
	Indicates if the column contains null elements in the range [begin, end), i.e., `null_count(begin, end) > 0` More...

bitmask_type const *	null_mask () const noexcept
	Returns raw pointer to the underlying bitmask allocation. More...

size_type	offset () const noexcept
	Returns the index of the first element relative to the base memory allocation, i.e., what is returned from `head<T>()`. More...

Friends
column_view	bit_cast (column_view const &input, data_type type)
	Zero-copy cast between types with the same size and compatible underlying representations. More...

Additional Inherited Members
Protected Member Functions inherited from cudf::detail::column_view_base
	column_view_base (column_view_base const &)=default
	Copy constructor.

	column_view_base (column_view_base &&)=default
	Move constructor.

column_view_base &	operator= (column_view_base const &)=default
	Copy assignment operator. More...

column_view_base &	operator= (column_view_base &&)=default
	Move assignment operator. More...

	column_view_base (data_type type, size_type size, void const data, bitmask_type const null_mask, size_type null_count, size_type offset=0)
	Construct a `column_view_base` from pointers to device memory for the elements and bitmask of the column. More...

Protected Attributes inherited from cudf::detail::column_view_base
data_type	_type {type_id::EMPTY}
	Element type.

size_type	_size {}
	Number of elements.

void const *	_data {}
	Pointer to device memory containing elements.

bitmask_type const *	_null_mask {}

size_type	_null_count {}
	The number of null elements.

size_type	_offset {}

Detailed Description

A non-owning, immutable view of device data as a column of elements, some of which may be null as indicated by a bitmask.

A column_view can be constructed implicitly from a cudf::column, or may be constructed explicitly from a pointer to pre-existing device memory.

Unless otherwise noted, the memory layout of the column_view's data and bitmask is expected to adhere to the Arrow Physical Memory Layout Specification: https://arrow.apache.org/docs/memory_layout.html

Because column_view is non-owning, no device memory is allocated nor freed when column_view objects are created or destroyed.

To enable zero-copy slicing, a column_view has an offset that indicates the index of the first element in the column relative to the base device memory allocation. By default, offset() is zero.

Definition at line 313 of file column_view.hpp.

Constructor & Destructor Documentation

◆ column_view() [1/2]

cudf::column_view::column_view	(	data_type	type,
		size_type	size,
		void const *	data,
		bitmask_type const *	null_mask,
		size_type	null_count,
		size_type	offset = `0`,
		std::vector< column_view > const &	children = `{}`
	)

Construct a column_view from pointers to device memory for the elements and bitmask of the column.

If null_count() is zero, null_mask is optional.

If type is EMPTY, the specified null_count will be ignored and null_count() will always return the same value as size()

Exceptions

cudf::logic_error	if `size < 0`
cudf::logic_error	if `size > 0` but `data == nullptr`
cudf::logic_error	if `type.id() == EMPTY` but `data != nullptr` or `null_mask != nullptr`
cudf::logic_error	if `null_count > 0`, but `null_mask == nullptr`
cudf::logic_error	if `offset < 0`

Parameters

type	The element type
size	The number of elements
data	Pointer to device memory containing the column elements
null_mask	Pointer to device memory containing the null indicator bitmask
null_count	The number of null elements.
offset	Optional, index of the first element
children	Optional, depending on the element type, child columns may contain additional data

◆ column_view() [2/2]

template<typename T , CUDF_ENABLE_IF(cudf::is_numeric< T >() or cudf::is_chrono< T >()) >

cudf::column_view::column_view ( device_span< T const > data )

inline

Construct a column view from a device_span<T>.

Only numeric and chrono types are supported.

Template Parameters

T	The device span type. Must be const and match the column view's type.

Parameters

data	A typed device span containing the column view's data.

Definition at line 420 of file column_view.hpp.

Member Function Documentation

◆ child()

column_view cudf::column_view::child ( size_type child_index ) const

inlinenoexcept

Returns the specified child.

Parameters

child_index The index of the desired child

Returns: The requested child column_view

Definition at line 385 of file column_view.hpp.

◆ child_begin()

auto cudf::column_view::child_begin ( ) const

inlinenoexcept

Returns iterator to the beginning of the ordered sequence of child column-views.

Returns: An iterator to a column_view referencing the first child column

Definition at line 402 of file column_view.hpp.

◆ child_end()

auto cudf::column_view::child_end ( ) const

inlinenoexcept

Returns iterator to the end of the ordered sequence of child column-views.

Returns: An iterator to a column_view one past the end of the child columns

Definition at line 409 of file column_view.hpp.

◆ num_children()

size_type cudf::column_view::num_children ( ) const

inlinenoexcept

Returns the number of child columns.

Returns: The number of child columns

Definition at line 395 of file column_view.hpp.

◆ operator device_span< T const >()

template<typename T , CUDF_ENABLE_IF(cudf::is_numeric< T >() or cudf::is_chrono< T >()) >

cudf::column_view::operator device_span< T const > ( ) const

inline

Converts a column view into a device span.

Only numeric and chrono data types are supported. The column view must not be nullable.

Template Parameters

T	The device span type. Must be const and match the column view's type.

Exceptions

cudf::logic_error	if the column view type does not match the span type.
cudf::logic_error	if the column view is nullable.

Returns: A typed device span of the column view's data.

Definition at line 442 of file column_view.hpp.

◆ operator=() [1/2]

column_view& cudf::column_view::operator= ( column_view && )

default

Move assignment operator.

Returns: Reference to this object

◆ operator=() [2/2]

column_view& cudf::column_view::operator= ( column_view const & )

default

Copy assignment operator.

Returns: Reference to this object

Friends And Related Function Documentation

◆ bit_cast

column_view bit_cast	(	column_view const &	input,
		data_type	type
	)

friend

Zero-copy cast between types with the same size and compatible underlying representations.

This is similar to reinterpret_cast or bit_cast in that it gives a view of the same raw bits as a different type. Unlike reinterpret_cast however, this cast is only allowed on types that have the same width and compatible representations. For example, the way timestamp types are laid out in memory is equivalent to an integer representing a duration since a fixed epoch; bit-casting to the same integer type (INT32 for days, INT64 for others) results in a raw view of the duration count. A FLOAT32 can also be bit-casted into INT32 and treated as an integer value. However, an INT32 column cannot be bit-casted to INT64 as the sizes differ, nor can a string_view column be casted into a numeric type column as their data representations are not compatible.

The validity of the conversion can be checked with cudf::is_bit_castable().

Exceptions

cudf::logic_error if the specified cast is not possible, i.e., is_bit_castable(input.type(), type) is false.

Parameters

input	The `column_view` to cast from
type	The `data_type` to cast to

Returns: New column_view wrapping the same data as input but cast to type

The documentation for this class was generated from the following file:

column_view.hpp

Public Member Functions

Friends

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ column_view() [1/2]

◆ column_view() [2/2]

Member Function Documentation

◆ child()

◆ child_begin()

◆ child_end()

◆ num_children()

◆ operator device_span< T const >()

◆ operator=() [1/2]

◆ operator=() [2/2]

Friends And Related Function Documentation

◆ bit_cast