histograms::Value_map< T > Class Template Reference

Value_map class. More...

#include <value_map.h>

Inheritance diagram for histograms::Value_map< T >:

Public Member Functions
	Value_map (const CHARSET_INFO *charset, Value_map_type data_type)
size_t	size () const override
	Returns the number of [value, count] pairs in the Value_map. More...
value_map_type::const_iterator	begin () const
value_map_type::const_iterator	end () const
bool	add_values (const T &value, const ha_rows count)
bool	insert (typename value_map_type::const_iterator begin, typename value_map_type::const_iterator end)
	Insert a range of values into the Value_map. More...
Histogram *	build_histogram (MEM_ROOT *mem_root, size_t num_buckets, const std::string &db_name, const std::string &tbl_name, const std::string &col_name) const override
	Create a Histogram from this Value_map. More...
size_t	element_overhead () const override
bool	add_values (const String &value, const ha_rows count)
Public Member Functions inherited from histograms::Value_map_base
	Value_map_base (const CHARSET_INFO *charset, Value_map_type data_type)
virtual	~Value_map_base ()=default
template<class T >
bool	add_values (const T &value, const ha_rows count)
	Add a value with the given count to this Value_map. More...
void	add_null_values (const ha_rows count)
	Increase the number of null values with the given count. More...
ha_rows	get_num_null_values () const
double	get_sampling_rate () const
void	set_sampling_rate (double sampling_rate)
	Set the sampling rate that was used to generate this Value_map. More...
const CHARSET_INFO *	get_character_set () const
Value_map_type	get_data_type () const

Private Types
using	value_map_type = std::map< T, ha_rows, Histogram_comparator, Mem_root_allocator< std::pair< const T, ha_rows > > >

Private Attributes
value_map_type	m_value_map

Additional Inherited Members
Protected Attributes inherited from histograms::Value_map_base
MEM_ROOT	m_mem_root

Detailed Description

template<class T>
class histograms::Value_map< T >

Value_map class.

This class works as a map. It is a collection of [key, count], where "count" is the number of occurrences of "key". The class abstracts away things like duplicate checking and the underlying container.

Member Typedef Documentation

value_map_type

template<class T >

using histograms::Value_map< T >::value_map_type = std::map<T, ha_rows, Histogram_comparator, Mem_root_allocator<std::pair<const T, ha_rows> >>

private

Constructor & Destructor Documentation

Value_map()

template<class T >

histograms::Value_map< T >::Value_map ( const CHARSET_INFO *  charset, Value_map_type  data_type  )

inline

Member Function Documentation

add_values() [1/2]

bool histograms::Value_map< String >::add_values	(	const String &	value,
		const ha_rows	count
	)

add_values() [2/2]

template<class T >

bool histograms::Value_map< T >::add_values	(	const T &	value,
		const ha_rows	count
	)

begin()

template<class T >

value_map_type::const_iterator histograms::Value_map< T >::begin ( void  ) const

inline

build_histogram()

template<class T >

Histogram * histograms::Value_map< T >::build_histogram ( MEM_ROOT *  mem_root, size_t  num_buckets, const std::string &  db_name, const std::string &  tbl_name, const std::string &  col_name  ) const

overridevirtual

Create a Histogram from this Value_map.

The resulting histogram will have at most "num_buckets" buckets (might be less), and all of its contents will be allocated on the supplied MEM_ROOT.

Parameters

mem_root	The MEM_ROOT to allocate the contents on
num_buckets	Maximum number of buckets to create
db_name	Database name
tbl_name	Table name
col_name	Column name

Returns

nullptr on error, or a valid histogram if success.

Implements histograms::Value_map_base.

element_overhead()

template<class T >

size_t histograms::Value_map< T >::element_overhead ( ) const

inlineoverridevirtual

Returns

the overhead in bytes for each distinct value stored in the Value_map. The value 32 is obtained from both GCC 8.2 and Clang 8.0 (same as sizeof(value_map_type::node_type) in C++17).

Implements histograms::Value_map_base.

end()

template<class T >

value_map_type::const_iterator histograms::Value_map< T >::end ( void  ) const

inline

insert()

template<class T >

bool histograms::Value_map< T >::insert	(	typename value_map_type::const_iterator	begin,
		typename value_map_type::const_iterator	end
	)

Insert a range of values into the Value_map.

Values in the range (begin, end] must be sorted according to Histogram_comparator. Note that this function is currently only used in unit testing.

Note

The value map must be empty before calling this function.

Parameters

begin	Iterator that points to the beginning of the range.
end	Iterator that points to the end of the range.

Returns

false on success, true on error (OOM or similar).

size()

template<class T >

size_t histograms::Value_map< T >::size ( ) const

inlineoverridevirtual

Returns the number of [value, count] pairs in the Value_map.

Returns

The number of values in the Value_map.

Implements histograms::Value_map_base.

Member Data Documentation

m_value_map

template<class T >

value_map_type histograms::Value_map< T >::m_value_map

private

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

• sql/histograms/histogram.h
• sql/histograms/value_map.h
• sql/histograms/value_map.cc