Bounded_queue< Element_type, Key_type, Key_generator, Key_compare > Class Template Reference

A priority queue with a fixed, limited size. More...

#include <bounded_queue.h>

Public Types
typedef Priority_queue< Key_type, std::vector< Key_type, Malloc_allocator< Key_type > >, Key_compare >	Queue_type
typedef Queue_type::allocator_type	allocator_type

Public Member Functions
	Bounded_queue (size_t element_size=sizeof(Element_type), const allocator_type &alloc=allocator_type(PSI_NOT_INSTRUMENTED))
bool	init (ha_rows max_elements, Key_generator *sort_param, Key_type *sort_keys)
	Initialize the queue. More...
template<class Opaque >
bool	push (const Opaque &opaque)
	Pushes an element on the queue. More...
size_t	num_elements () const
	The number of elements in the queue. More...

Private Attributes
Queue_type	m_queue
Key_type *	m_sort_keys
Key_generator *	m_sort_param
size_t	m_element_size

Detailed Description

template<typename Element_type, typename Key_type, typename Key_generator, typename Key_compare = std::less<Key_type>>
class Bounded_queue< Element_type, Key_type, Key_generator, Key_compare >

A priority queue with a fixed, limited size.

This is a wrapper on top of Priority_queue. It keeps the top-N elements which are inserted.

Elements of type Element_type are pushed into the queue. For each element, we call a user-supplied Key_generator::make_sortkey(), to generate a key of type Key_type for the element. Instances of Key_type are compared with the user-supplied Key_compare.

Pointers to the top-N elements are stored in the sort_keys array given to the init() function below. To access elements in sorted order, sort the array and access it sequentially.

Member Typedef Documentation

allocator_type

template<typename Element_type , typename Key_type , typename Key_generator , typename Key_compare = std::less<Key_type>>

typedef Queue_type::allocator_type Bounded_queue< Element_type, Key_type, Key_generator, Key_compare >::allocator_type

Queue_type

template<typename Element_type , typename Key_type , typename Key_generator , typename Key_compare = std::less<Key_type>>

typedef Priority_queue< Key_type, std::vector<Key_type, Malloc_allocator<Key_type> >, Key_compare> Bounded_queue< Element_type, Key_type, Key_generator, Key_compare >::Queue_type

Constructor & Destructor Documentation

Bounded_queue()

template<typename Element_type , typename Key_type , typename Key_generator , typename Key_compare = std::less<Key_type>>

Bounded_queue< Element_type, Key_type, Key_generator, Key_compare >::Bounded_queue ( size_t  element_size = sizeof(Element_type), const allocator_type &  alloc = allocator_type(PSI_NOT_INSTRUMENTED)  )

inline

Member Function Documentation

init()

template<typename Element_type , typename Key_type , typename Key_generator , typename Key_compare = std::less<Key_type>>

bool Bounded_queue< Element_type, Key_type, Key_generator, Key_compare >::init ( ha_rows  max_elements, Key_generator *  sort_param, Key_type *  sort_keys  )

inline

Initialize the queue.

Parameters

	max_elements	The size of the queue.
	sort_param	Sort parameters. We call sort_param->make_sortkey() to generate keys for elements.
[in,out]	sort_keys	Array of keys to sort. Must be initialized by caller. Will be filled with pointers to the top-N elements.

Return values

false

OK, true Could not allocate memory.

We do not take ownership of any of the input pointer arguments.

num_elements()

template<typename Element_type , typename Key_type , typename Key_generator , typename Key_compare = std::less<Key_type>>

size_t Bounded_queue< Element_type, Key_type, Key_generator, Key_compare >::num_elements ( ) const

inline

The number of elements in the queue.

push()

template<typename Element_type , typename Key_type , typename Key_generator , typename Key_compare = std::less<Key_type>>

template<class Opaque >

bool Bounded_queue< Element_type, Key_type, Key_generator, Key_compare >::push ( const Opaque &  opaque )

inline

Pushes an element on the queue.

If the queue is already full, we discard one element. Calls m_sort_param::make_sortkey() to generate a key for the element.

Parameters

opaque

Parameter to send on to make_sortkey().

Return values

false

OK, true error.

Member Data Documentation

m_element_size

template<typename Element_type , typename Key_type , typename Key_generator , typename Key_compare = std::less<Key_type>>

size_t Bounded_queue< Element_type, Key_type, Key_generator, Key_compare >::m_element_size

private

m_queue

template<typename Element_type , typename Key_type , typename Key_generator , typename Key_compare = std::less<Key_type>>

Queue_type Bounded_queue< Element_type, Key_type, Key_generator, Key_compare >::m_queue

private

m_sort_keys

template<typename Element_type , typename Key_type , typename Key_generator , typename Key_compare = std::less<Key_type>>

Key_type* Bounded_queue< Element_type, Key_type, Key_generator, Key_compare >::m_sort_keys

private

m_sort_param

template<typename Element_type , typename Key_type , typename Key_generator , typename Key_compare = std::less<Key_type>>

Key_generator* Bounded_queue< Element_type, Key_type, Key_generator, Key_compare >::m_sort_param

private

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

• sql/bounded_queue.h