Combining

Files
file	strings/combine.hpp
	Strings APIs for concatenate and join.

Enumerations
enum class	cudf::strings::separator_on_nulls { cudf::strings::YES , cudf::strings::NO }
	Setting for specifying how separators are added with null strings elements. More...
enum class	cudf::strings::output_if_empty_list { cudf::strings::EMPTY_STRING , cudf::strings::NULL_ELEMENT }
	Setting for specifying what will be output from join_list_elements when an input list is empty. More...

Functions
std::unique_ptr< column >	cudf::strings::join_strings (strings_column_view const &input, string_scalar const &separator=string_scalar(""), string_scalar const &narep=string_scalar("", false), rmm::cuda_stream_view stream=cudf::get_default_stream(), rmm::mr::device_memory_resource *mr=rmm::mr::get_current_device_resource())
	Concatenates all strings in the column into one new string delimited by an optional separator string. More...
std::unique_ptr< column >	cudf::strings::concatenate (table_view const &strings_columns, strings_column_view const &separators, string_scalar const &separator_narep=string_scalar("", false), string_scalar const &col_narep=string_scalar("", false), separator_on_nulls separate_nulls=separator_on_nulls::YES, rmm::cuda_stream_view stream=cudf::get_default_stream(), rmm::mr::device_memory_resource *mr=rmm::mr::get_current_device_resource())
	Concatenates a list of strings columns using separators for each row and returns the result as a strings column. More...
std::unique_ptr< column >	cudf::strings::concatenate (table_view const &strings_columns, string_scalar const &separator=string_scalar(""), string_scalar const &narep=string_scalar("", false), separator_on_nulls separate_nulls=separator_on_nulls::YES, rmm::cuda_stream_view stream=cudf::get_default_stream(), rmm::mr::device_memory_resource *mr=rmm::mr::get_current_device_resource())
	Row-wise concatenates the given list of strings columns and returns a single strings column result. More...
std::unique_ptr< column >	cudf::strings::join_list_elements (lists_column_view const &lists_strings_column, strings_column_view const &separators, string_scalar const &separator_narep=string_scalar("", false), string_scalar const &string_narep=string_scalar("", false), separator_on_nulls separate_nulls=separator_on_nulls::YES, output_if_empty_list empty_list_policy=output_if_empty_list::EMPTY_STRING, rmm::cuda_stream_view stream=cudf::get_default_stream(), rmm::mr::device_memory_resource *mr=rmm::mr::get_current_device_resource())
	Given a lists column of strings (each row is a list of strings), concatenates the strings within each row and returns a single strings column result. More...
std::unique_ptr< column >	cudf::strings::join_list_elements (lists_column_view const &lists_strings_column, string_scalar const &separator=string_scalar(""), string_scalar const &narep=string_scalar("", false), separator_on_nulls separate_nulls=separator_on_nulls::YES, output_if_empty_list empty_list_policy=output_if_empty_list::EMPTY_STRING, rmm::cuda_stream_view stream=cudf::get_default_stream(), rmm::mr::device_memory_resource *mr=rmm::mr::get_current_device_resource())
	Given a lists column of strings (each row is a list of strings), concatenates the strings within each row and returns a single strings column result. More...

Detailed Description

Enumeration Type Documentation

output_if_empty_list

enum cudf::strings::output_if_empty_list

strong

Setting for specifying what will be output from join_list_elements when an input list is empty.

Enumerator
EMPTY_STRING	Empty list will result in empty string.
NULL_ELEMENT	Empty list will result in a null.

Definition at line 48 of file strings/combine.hpp.

separator_on_nulls

enum cudf::strings::separator_on_nulls

strong

Setting for specifying how separators are added with null strings elements.

Enumerator
YES	Always add separators between elements.
NO	Do not add separators if an element is null.

Definition at line 39 of file strings/combine.hpp.

Function Documentation

concatenate() [1/2]

std::unique_ptr<column> cudf::strings::concatenate	(	table_view const &	strings_columns,
		string_scalar const &	separator = string_scalar(""),
		string_scalar const &	narep = string_scalar("", false),
		separator_on_nulls	separate_nulls = separator_on_nulls::YES,
		rmm::cuda_stream_view	stream = cudf::get_default_stream(),
		rmm::mr::device_memory_resource *	mr = rmm::mr::get_current_device_resource()
	)

Row-wise concatenates the given list of strings columns and returns a single strings column result.

Each new string is created by concatenating the strings from the same row delimited by the separator provided.

Any row with a null entry will result in the corresponding output row to be null entry unless a narep string is specified to be used in its place.

If separate_nulls is set to NO and narep is valid then separators are not added to the output between null elements. Otherwise, separators are always added if narep is valid.

More than one column must be specified in the input strings_columns table.

Example:
s1 = ['aa', null, '', 'dd']
s2 = ['', 'bb', 'cc', null]
out = concatenate({s1, s2})
out is ['aa', null, 'cc', null]
 
out = concatenate({s1, s2}, ':', '_')
out is ['aa:', '_:bb', ':cc', 'dd:_']
 
out = concatenate({s1, s2}, ':', '', separator_on_nulls::NO)
out is ['aa:', 'bb', ':cc', 'dd']

Exceptions

cudf::logic_error	if input columns are not all strings columns.
cudf::logic_error	if separator is not valid.
cudf::logic_error	if only one column is specified

Parameters

strings_columns	List of string columns to concatenate
separator	String that should inserted between each string from each row. Default is an empty string.
narep	String to replace any null strings found in any column. Default of invalid-scalar means any null entry in any column will produces a null result for that row.
separate_nulls	If YES, then the separator is included for null rows if narep is valid
stream	CUDA stream used for device memory operations and kernel launches
mr	Device memory resource used to allocate the returned column's device memory

Returns

New column with concatenated results

concatenate() [2/2]

std::unique_ptr<column> cudf::strings::concatenate	(	table_view const &	strings_columns,
		strings_column_view const &	separators,
		string_scalar const &	separator_narep = string_scalar("", false),
		string_scalar const &	col_narep = string_scalar("", false),
		separator_on_nulls	separate_nulls = separator_on_nulls::YES,
		rmm::cuda_stream_view	stream = cudf::get_default_stream(),
		rmm::mr::device_memory_resource *	mr = rmm::mr::get_current_device_resource()
	)

Concatenates a list of strings columns using separators for each row and returns the result as a strings column.

Each new string is created by concatenating the strings from the same row delimited by the row separator provided for that row. The following rules are applicable:

• If row separator for a given row is null, output column for that row is null, unless there is a valid separator_narep
• The separator is applied between two output row values if the separate_nulls is YES or only between valid rows if separate_nulls is NO.
• If separator_narep and col_narep are both valid, the output column is always non nullable

Example:
c0   = ['aa', null, '',  'ee',  null, 'ff']
c1   = [null, 'cc', 'dd', null, null, 'gg']
c2   = ['bb', '',   null, null, null, 'hh']
sep  = ['::', '%%', '^^', '!',  '*',  null]
out = concatenate({c0, c1, c2}, sep)
// all rows have at least one null or sep[i]==null
out is [null, null, null, null, null, null]
 
sep_rep = '+'
out = concatenate({c0, c1, c2}, sep, sep_rep)
// all rows with at least one null output as null
out is [null, null, null, null, null, 'ff+gg+hh']
 
col_narep = '-'
sep_na = non-valid scalar
out = concatenate({c0, c1, c2}, sep, sep_na, col_narep)
// only the null entry in the sep column produces a null row
out is ['aa::-::bb', '-%%cc%%', '^^dd^^-', 'ee!-!-', '-*-*-', null]
 
col_narep = ''
out = concatenate({c0, c1, c2}, sep, sep_rep, col_narep, separator_on_nulls:NO)
// parameter suppresses separator for null rows
out is ['aa::bb', 'cc%%', '^^dd', 'ee', '', 'ff+gg+hh']

Exceptions

cudf::logic_error	if no input columns are specified - table view is empty
cudf::logic_error	if input columns are not all strings columns.
cudf::logic_error	if the number of rows from separators and strings_columns do not match

Parameters

strings_columns	List of strings columns to concatenate
separators	Strings column that provides the separator for a given row
separator_narep	String to replace a null separator for a given row. Default of invalid-scalar means no row separator value replacements.
col_narep	String that should be used in place of any null strings found in any column. Default of invalid-scalar means no null column value replacements.
separate_nulls	If YES, then the separator is included for null rows if col_narep is valid.
stream	CUDA stream used for device memory operations and kernel launches
mr	Resource for allocating device memory

Returns

New column with concatenated results

join_list_elements() [1/2]

std::unique_ptr<column> cudf::strings::join_list_elements	(	lists_column_view const &	lists_strings_column,
		string_scalar const &	separator = string_scalar(""),
		string_scalar const &	narep = string_scalar("", false),
		separator_on_nulls	separate_nulls = separator_on_nulls::YES,
		output_if_empty_list	empty_list_policy = output_if_empty_list::EMPTY_STRING,
		rmm::cuda_stream_view	stream = cudf::get_default_stream(),
		rmm::mr::device_memory_resource *	mr = rmm::mr::get_current_device_resource()
	)

Given a lists column of strings (each row is a list of strings), concatenates the strings within each row and returns a single strings column result.

Each new string is created by concatenating the strings from the same row (same list element) delimited by the separator provided.

A null list row will always result in a null string in the output row. Any non-null list row having a null element will result in the corresponding output row to be null unless a narep string is specified to be used in its place.

If separate_nulls is set to NO and narep is valid then separators are not added to the output between null elements. Otherwise, separators are always added if narep is valid.

If empty_list_policy is set to EMPTY_STRING, any row that is an empty list will result in an empty output string. Otherwise, the output will be a null.

In the special case when the input list row contains all null elements, the output will be the same as in case of empty input list regardless of narep and separate_nulls values.

Example:
s = [ ['aa', 'bb', 'cc'], null, ['', 'dd'], ['ee', null], ['ff'] ]
 
out = join_list_elements(s)
out is ['aabbcc', null, 'dd', null, 'ff']
 
out = join_list_elements(s, ':', '_')
out is ['aa:bb:cc', null,  ':dd', 'ee:_', 'ff']
 
out = join_list_elements(s, ':', '', separator_on_nulls::NO)
out is ['aa:bb:cc', null,  ':dd', 'ee', 'ff']

Exceptions

cudf::logic_error	if input column is not lists of strings column.
cudf::logic_error	if separator is not valid.

Parameters

lists_strings_column	Column containing lists of strings to concatenate
separator	String to insert between strings of each list row. Default is an empty string.
narep	String to replace null strings in any non-null list row. Default is an invalid-scalar denoting that list rows containing null strings will result in a null string in the corresponding output rows.
separate_nulls	If YES, then the separator is included for null rows if narep is valid
empty_list_policy	If set to EMPTY_STRING, any input row that is an empty list will result in an empty string. Otherwise, it will result in a null.
stream	CUDA stream used for device memory operations and kernel launches
mr	Device memory resource used to allocate the returned column's device memory

Returns

New strings column with concatenated results

join_list_elements() [2/2]

std::unique_ptr<column> cudf::strings::join_list_elements	(	lists_column_view const &	lists_strings_column,
		strings_column_view const &	separators,
		string_scalar const &	separator_narep = string_scalar("", false),
		string_scalar const &	string_narep = string_scalar("", false),
		separator_on_nulls	separate_nulls = separator_on_nulls::YES,
		output_if_empty_list	empty_list_policy = output_if_empty_list::EMPTY_STRING,
		rmm::cuda_stream_view	stream = cudf::get_default_stream(),
		rmm::mr::device_memory_resource *	mr = rmm::mr::get_current_device_resource()
	)

Given a lists column of strings (each row is a list of strings), concatenates the strings within each row and returns a single strings column result.

Each new string is created by concatenating the strings from the same row (same list element) delimited by the row separator provided in the separators strings column.

A null list row will always result in a null string in the output row. Any non-null list row having a null element will result in the corresponding output row to be null unless a valid string_narep scalar is provided to be used in its place. Any null row in the separators column will also result in a null output row unless a valid separator_narep scalar is provided to be used in place of the null separators.

If separate_nulls is set to NO and string_narep is valid then separators are not added to the output between null elements. Otherwise, separators are always added if string_narep is valid.

If empty_list_policy is set to EMPTY_STRING, any row that is an empty list will result in an empty output string. Otherwise, the output will be a null.

In the special case when the input list row contains all null elements, the output will be the same as in case of empty input list regardless of string_narep and separate_nulls values.

Example:
s = [ ['aa', 'bb', 'cc'], null, ['', 'dd'], ['ee', null], ['ff', 'gg'] ]
sep  = ['::', '%%',  '!',  '*',  null]
 
out = join_list_elements(s, sep)
out is ['aa::bb::cc', null, '!dd', null, null]
 
out = join_list_elements(s, sep, ':', '_')
out is ['aa::bb::cc', null,  '!dd', 'ee*_', 'ff:gg']
 
out = join_list_elements(s, sep, ':', '', separator_on_nulls::NO)
out is ['aa::bb::cc', null,  '!dd', 'ee', 'ff:gg']

Exceptions

cudf::logic_error	if input column is not lists of strings column.
cudf::logic_error	if the number of rows from separators and lists_strings_column do not match

Parameters

lists_strings_column	Column containing lists of strings to concatenate
separators	Strings column that provides separators for concatenation
separator_narep	String that should be used to replace a null separator. Default is an invalid-scalar denoting that rows containing null separator will result in a null string in the corresponding output rows.
string_narep	String to replace null strings in any non-null list row. Default is an invalid-scalar denoting that list rows containing null strings will result in a null string in the corresponding output rows.
separate_nulls	If YES, then the separator is included for null rows if narep is valid
empty_list_policy	If set to EMPTY_STRING, any input row that is an empty list will result in an empty string. Otherwise, it will result in a null.
stream	CUDA stream used for device memory operations and kernel launches
mr	Device memory resource used to allocate the returned column's device memory

Returns

New strings column with concatenated results

join_strings()

std::unique_ptr<column> cudf::strings::join_strings	(	strings_column_view const &	input,
		string_scalar const &	separator = string_scalar(""),
		string_scalar const &	narep = string_scalar("", false),
		rmm::cuda_stream_view	stream = cudf::get_default_stream(),
		rmm::mr::device_memory_resource *	mr = rmm::mr::get_current_device_resource()
	)

Concatenates all strings in the column into one new string delimited by an optional separator string.

This returns a column with one string. Any null entries are ignored unless the narep parameter specifies a replacement string.

Example:
s = ['aa', null, '', 'zz' ]
r = join_strings(s,':','_')
r is ['aa:_::zz']

Exceptions

cudf::logic_error

if separator is not valid.

Parameters

input	Strings for this operation
separator	String that should inserted between each string. Default is an empty string.
narep	String to replace any null strings found. Default of invalid-scalar will ignore any null entries.
stream	CUDA stream used for device memory operations and kernel launches
mr	Device memory resource used to allocate the returned column's device memory.

Returns

New column containing one string.