JASS::index_postings_impact Class Reference

Holder class for an impact ordered postings list. More...

#include <index_postings_impact.h>

Collaboration diagram for JASS::index_postings_impact:

Classes
class	impact
	Each impact is represented as an impact score, and a start and end pointer. More...
class	reverse_iterator
	A reverse iterator for iterating over impact headers from highet to lowest. More...

Public Types
typedef uint16_t	impact_type
	An impact value (i.e. a term frequency value) is of this type.

Public Member Functions
	index_postings_impact (size_t document_count, allocator &memory)
	Constructor. More...
void	set_impact_count (size_t number_of_impacts)
	Tell this object how many impacts it holds. More...
compress_integer::integer *	get_postings (void)
	Return a pointer to the buffer containing the postings. More...
compress_integer::integer &	operator[] (size_t index) const
	return a reference to the size_t at position index in the postings array. More...
void	header (size_t index, impact_type score, compress_integer::integer *postings_start, compress_integer::integer *postings_end)
	Set the value of the impact header object at the given index. More...
size_t	impact_size (void) const
	Return the number of unique impact scores in the postings list. More...
const impact *	begin (void) const
	Return a pointer to the first impact header (for use in an iterator). More...
const impact *	end (void) const
	Return a pointer to one element past the end of the impact headers (for use in an iterator). More...
const auto	rbegin (void) const
	Return a pointer to the last impact header (for use in an reverse iterator). More...
const auto	rend (void) const
	Return a pointer to one element before the first impact headers (for use in reverse iteration iterator). More...
void	text_render (std::ostream &stream)
	Dump a human-readable version of the postings list down the stream. More...

Static Public Member Functions
static void	unittest (void)
	Unit test this class.

Static Public Attributes
static constexpr size_t	largest_impact = 1024
	The largest allowable immpact score (255 is an good value).
static constexpr size_t	smallest_impact = 1
	The smallest allowable impact score (normally 1)

Protected Attributes
allocator &	memory
	All allocation happens in this arena.
size_t	number_of_impacts
	The number of impact objects in the impacts array.
impact	impacts [largest_impact+1]
	List of impact pointers (the impact header).
size_t	number_of_postings
	The length of the postings array measured in size_t.
compress_integer::integer *	postings
	The list of document IDs, strung together for each postings segment.
compress_integer::integer *	document_ids
	The re-used buffer storing decoded document ids - used while impact ordering.
index_postings_impact::impact_type *	term_frequencies
	The re-used buffer storing the term frequencies - used while impact ordering.
size_t	temporary_size
	The number of bytes in temporary.
uint8_t *	temporary
	Temporary buffer - cannot be used to store anything between calls.

Friends
class	index_postings

Detailed Description

Holder class for an impact ordered postings list.

Constructor & Destructor Documentation

index_postings_impact()

JASS::index_postings_impact::index_postings_impact ( size_t  document_count, allocator &  memory  )

inline

Constructor.

The postings lists are typvically stored <impact><d><d>...<d><0>, The headers point to the list of <d>s (not the <impact> or the <0>.

Parameters

document_count	[in] The number of documents in the collection (the length of the longest postings list)
memory	[in] All memory allocation happens in this arena

Member Function Documentation

begin()

const impact* JASS::index_postings_impact::begin ( void  ) const

inline

Return a pointer to the first impact header (for use in an iterator).

Returns

A pointer to the first impact header.

end()

const impact* JASS::index_postings_impact::end ( void  ) const

inline

Return a pointer to one element past the end of the impact headers (for use in an iterator).

Returns

A pointer to one element past the end of the impact headers.

get_postings()

compress_integer::integer* JASS::index_postings_impact::get_postings ( void  )

inline

Return a pointer to the buffer containing the postings.

This method should only be called by a method that builds one of these objects.

header()

void JASS::index_postings_impact::header ( size_t  index, impact_type  score, compress_integer::integer *  postings_start, compress_integer::integer *  postings_end  )

inline

Set the value of the impact header object at the given index.

Parameters

index	[in] Which header to set
score	[in] The impact value for all the documents in this range
postings_start	[in] The start of the range of postings that share this impact score
postings_end	[in] The end of the range if postings that share this impact score

impact_size()

size_t JASS::index_postings_impact::impact_size ( void  ) const

inline

Return the number of unique impact scores in the postings list.

The number of unique impact scores.

operator[]()

compress_integer::integer& JASS::index_postings_impact::operator[] ( size_t  index ) const

inline

return a reference to the size_t at position index in the postings array.

Node taht this is astrict index and not range checked. Access out of range ill resilt in undefined behaviour. The access is to elements in the array so if the postings are stored <impact><d><d>...<d><0> then posting[0] will be the impact score.

Returns

a reference to the size_t at postng[index].

rbegin()

const auto JASS::index_postings_impact::rbegin ( void  ) const

inline

Return a pointer to the last impact header (for use in an reverse iterator).

Returns

A pointer to the first impact header.

rend()

const auto JASS::index_postings_impact::rend ( void  ) const

inline

Return a pointer to one element before the first impact headers (for use in reverse iteration iterator).

Returns

A pointer to one element past the end of the impact headers.

set_impact_count()

void JASS::index_postings_impact::set_impact_count ( size_t  number_of_impacts )

inline

Tell this object how many impacts it holds.

This method should only be called by a method that builds one of these objects.

Parameters

number_of_impacts

[in] The number of impact segments this object holds

text_render()

void JASS::index_postings_impact::text_render ( std::ostream &  stream )

inline

Dump a human-readable version of the postings list down the stream.

Parameters

stream

[in] The stream to write to.

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

• source/index_postings_impact.h