meta::index::vocabulary_map Class Reference

A read-only view of a B+-tree-like structure that stores the vocabulary for an index. More...

#include <vocabulary_map.h>

Public Member Functions
	vocabulary_map (const std::string &path, uint16_t block_size=4096)
	Creates a vocabulary map reading the file in the given path with the given block size. More...
	vocabulary_map (vocabulary_map &&)=default
	Move constructs a vocabulary_map.
vocabulary_map &	operator= (vocabulary_map &&)=default
	Move assigns a vocabulary_map.
util::optional< term_id >	find (const std::string &term) const
	Finds the given term in the tree, if it exists. More...
std::string	find_term (term_id t_id) const
	Finds the term associated with the given id. More...
uint64_t	size () const
	The number of terms in the map.

Private Member Functions
int	compare (const std::string &term, const char *other) const
	Convenience wrapper for comparing the term with strings in the tree. More...

Private Attributes
io::mmap_file	file_
	The file containing the tree. More...
util::disk_vector< uint64_t >	inverse_
	Byte positions for each term in the leaves to allow for reverse lookup of a the string associated with a given id.
uint64_t	block_size_
	The size of the nodes in the tree.
uint64_t	leaf_end_pos_
	The ending position of the leaf nodes. More...
uint64_t	initial_seek_pos_
	The position of the first internal node that is not the root. More...

Detailed Description

A read-only view of a B+-tree-like structure that stores the vocabulary for an index.

It reads the file format that is written by the vocabulary_map_writer class (see the documentation for the writer for information about the file format).

Constructor & Destructor Documentation

meta::index::vocabulary_map::vocabulary_map	(	const std::string &	path,
		uint16_t	block_size = 4096
	)

Creates a vocabulary map reading the file in the given path with the given block size.

Changing the block size is not recommended—the block size used should always be the same as the block size used in the vocabulary_map_writer used to create the tree.

Parameters

path	the location of the tree file
block_size	the size of the nodes in the tree

Member Function Documentation

int meta::index::vocabulary_map::compare ( const std::string &  term, const char *  other  ) const

private

Convenience wrapper for comparing the term with strings in the tree.

Parameters

term	the term we are looking for
other	the string in the tree we are considering

util::optional< term_id > meta::index::vocabulary_map::find

(

const std::string &

term

)

const

Finds the given term in the tree, if it exists.

Parameters

term	the term to find an id for

std::string meta::index::vocabulary_map::find_term

(

term_id

t_id

)

const

Finds the term associated with the given id.

No bounds checking is performed—accessing beyond the maximum assigned term_id is undefined behavior.

Parameters

t_id	the term id to find the string representation of

Member Data Documentation

io::mmap_file meta::index::vocabulary_map::file_

private

The file containing the tree.

mmapped for performance.

uint64_t meta::index::vocabulary_map::leaf_end_pos_

private

The ending position of the leaf nodes.

Used to determine when to stop a search.

uint64_t meta::index::vocabulary_map::initial_seek_pos_

private

The position of the first internal node that is not the root.

Used to seek to the first level during search.

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

• /home/chase/projects/meta/include/index/vocabulary_map.h
• /home/chase/projects/meta/src/index/vocabulary_map.cpp