histograms::Histogram_comparator Struct Reference

Histogram comparator. More...

#include <value_map.h>

Public Member Functions
template<class T >
bool	operator() (const T &lhs, const T &rhs) const
	Overload operator(), so that we can use this struct as a custom comparator in std classes/functions. More...
template<class T >
bool	operator() (const equi_height::Bucket< T > &a, const T &b) const
	Used by std::lower_bound when computing equal-to and less-than selectivity to find the first bucket with an upper bound that is not less than b. More...
template<class T >
bool	operator() (const SingletonBucket< T > &a, const T &b) const
	Same as above, but for singleton histogram buckets. More...
template<class T >
bool	operator() (const T &a, const equi_height::Bucket< T > &b) const
	Used by std::upper_bound when computing greater-than selectivity in order to find the first bucket with an upper bound that is greater than a. More...
template<class T >
bool	operator() (const T &a, const SingletonBucket< T > &b) const
	Same as above, but for singleton histogram buckets. More...
template<class T >
bool	operator() (const equi_height::Bucket< T > &a, const equi_height::Bucket< T > &b) const
	Used by std::is_sorted to verify that equi-height histogram buckets are stored in sorted order. More...
template<class T >
bool	operator() (const SingletonBucket< T > &a, const SingletonBucket< T > &b) const
	Same as above, but for singleton histogram buckets. More...
template<>
bool	operator() (const String &lhs, const String &rhs) const
template<>
bool	operator() (const MYSQL_TIME &lhs, const MYSQL_TIME &rhs) const
template<>
bool	operator() (const my_decimal &lhs, const my_decimal &rhs) const

Detailed Description

Histogram comparator.

Typical usage is in a "value map", where we for instance need to sort based on string collation and similar.

Member Function Documentation

operator()() [1/10]

template<class T >

bool histograms::Histogram_comparator::operator() ( const equi_height::Bucket< T > &  a, const equi_height::Bucket< T > &  b  ) const

inline

Used by std::is_sorted to verify that equi-height histogram buckets are stored in sorted order.

We consider bucket a = [a1, a2] to be less than bucket b = [b1, b2] if a2 < b1.

operator()() [2/10]

template<class T >

bool histograms::Histogram_comparator::operator() ( const equi_height::Bucket< T > &  a, const T &  b  ) const

inline

Used by std::lower_bound when computing equal-to and less-than selectivity to find the first bucket with an upper bound that is not less than b.

operator()() [3/10]

template<>

bool histograms::Histogram_comparator::operator()	(	const my_decimal &	lhs,
		const my_decimal &	rhs
	)		const

operator()() [4/10]

template<>

bool histograms::Histogram_comparator::operator()	(	const MYSQL_TIME &	lhs,
		const MYSQL_TIME &	rhs
	)		const

operator()() [5/10]

template<class T >

bool histograms::Histogram_comparator::operator() ( const SingletonBucket< T > &  a, const SingletonBucket< T > &  b  ) const

inline

Same as above, but for singleton histogram buckets.

operator()() [6/10]

template<class T >

bool histograms::Histogram_comparator::operator() ( const SingletonBucket< T > &  a, const T &  b  ) const

inline

Same as above, but for singleton histogram buckets.

operator()() [7/10]

template<>

bool histograms::Histogram_comparator::operator()	(	const String &	lhs,
		const String &	rhs
	)		const

operator()() [8/10]

template<class T >

bool histograms::Histogram_comparator::operator() ( const T &  a, const equi_height::Bucket< T > &  b  ) const

inline

Used by std::upper_bound when computing greater-than selectivity in order to find the first bucket with an upper bound that is greater than a.

Notice that the comparison function used by std::lower_bound and std::upper_bound have the collection element as the first and second argument, respectively.

operator()() [9/10]

template<class T >

bool histograms::Histogram_comparator::operator() ( const T &  a, const SingletonBucket< T > &  b  ) const

inline

Same as above, but for singleton histogram buckets.

operator()() [10/10]

template<class T >

bool histograms::Histogram_comparator::operator() ( const T &  lhs, const T &  rhs  ) const

inline

Overload operator(), so that we can use this struct as a custom comparator in std classes/functions.

Parameters

lhs	first value to compare
rhs	second value to compare

Returns

true if lhs is considered to be smaller/less than rhs. false otherwise.

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

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