var_opt_union< T, A > Class Template Reference

Provides a unioning operation over var_opt_sketch objects. More...

#include <var_opt_union.hpp>

Public Member Functions
void	update (const var_opt_sketch< T, A > &sk)
	Updates this union with the given sketch This method takes an lvalue. More...
void	update (var_opt_sketch< T, A > &&sk)
	Updates this union with the given sketch This method takes an rvalue. More...
var_opt_sketch< T, A >	get_result () const
	Gets the varopt sketch resulting from the union of any input sketches. More...
void	reset ()
	Resets the union to its default, empty state.
template<typename SerDe = serde<T>>
size_t	get_serialized_size_bytes (const SerDe &sd=SerDe()) const
	Computes size needed to serialize the current state of the union. More...
template<typename SerDe = serde<T>>
vector_bytes	serialize (unsigned header_size_bytes=0, const SerDe &sd=SerDe()) const
	NOTE: This method may be deprecated in a future version. More...
template<typename SerDe = serde<T>>
void	serialize (std::ostream &os, const SerDe &sd=SerDe()) const
	NOTE: This method may be deprecated in a future version. More...
string< A >	to_string () const
	Prints a summary of the union as a string. More...

Static Public Member Functions
template<typename SerDe = serde<T>>
static var_opt_union	deserialize (std::istream &is, const SerDe &sd=SerDe(), const A &allocator=A())
	NOTE: This method may be deprecated in a future version. More...
template<typename SerDe = serde<T>>
static var_opt_union	deserialize (const void *bytes, size_t size, const SerDe &sd=SerDe(), const A &allocator=A())
	NOTE: This method may be deprecated in a future version. More...

Detailed Description

template<typename T, typename A = std::allocator<T>>
class datasketches::var_opt_union< T, A >

Provides a unioning operation over var_opt_sketch objects.

This union allows the sample size k to float, possibly increasing or decreasing as warranted by the available data.

The union currently allows serialization and deserialization, even though transporting union objects seems to be an anti-pattern with most sketches. We currently provide it here because the get_result() call may need to discard samples and decrease k in order to return a valid sketch, even if future calls to update() would allow k to remain larger.

The (de)serialization methods may be deprecated and subsequently removed in future versions.

author Kevin Lang author Jon Malkin

Member Function Documentation

update() [1/2]

void update

(

const var_opt_sketch< T, A > &

sk

)

Updates this union with the given sketch This method takes an lvalue.

Parameters

sk	a sketch to add to the union

update() [2/2]

void update

(

var_opt_sketch< T, A > &&

sk

)

Updates this union with the given sketch This method takes an rvalue.

Parameters

sk	a sketch to add to the union

get_result()

var_opt_sketch< T, A > get_result

Gets the varopt sketch resulting from the union of any input sketches.

Returns

a varopt sketch

get_serialized_size_bytes()

size_t get_serialized_size_bytes

(

const SerDe &

sd = SerDe()

)

const

Computes size needed to serialize the current state of the union.

This version is for all other types and can be expensive since every item needs to be looked at.

Parameters

sd	instance of a SerDe

Returns

size in bytes needed to serialize this sketch

serialize() [1/2]

vector_bytes serialize	(	unsigned	header_size_bytes = 0,
		const SerDe &	sd = SerDe()
	)		const

NOTE: This method may be deprecated in a future version.

This method serializes the sketch as a vector of bytes. An optional header can be reserved in front of the sketch. It is a blank space of a given size. This header is used in Datasketches PostgreSQL extension.

Parameters

header_size_bytes	space to reserve in front of the sketch
sd	instance of a SerDe

serialize() [2/2]

void serialize	(	std::ostream &	os,
		const SerDe &	sd = SerDe()
	)		const

NOTE: This method may be deprecated in a future version.

This method serializes the sketch into a given stream in a binary form

Parameters

os	output stream
sd	instance of a SerDe

deserialize() [1/2]

static var_opt_union deserialize ( std::istream &  is, const SerDe &  sd = SerDe(), const A &  allocator = A()  )

static

NOTE: This method may be deprecated in a future version.

This method deserializes a union from a given stream.

Parameters

is	input stream
sd	instance of a SerDe
allocator	instance of an Allocator

Returns

an instance of a union

deserialize() [2/2]

static var_opt_union deserialize ( const void *  bytes, size_t  size, const SerDe &  sd = SerDe(), const A &  allocator = A()  )

static

NOTE: This method may be deprecated in a future version.

This method deserializes a union from a given array of bytes.

Parameters

bytes	pointer to the array of bytes
size	the size of the array
sd	instance of a SerDe
allocator	instance of an Allocator

Returns

an instance of a union

to_string()

string< A > to_string

Prints a summary of the union as a string.

Returns

the summary as a string

---

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

• sampling/include/var_opt_sketch.hpp
• sampling/include/var_opt_union.hpp
• sampling/include/var_opt_union_impl.hpp