250 lines
7.6 KiB
C++
250 lines
7.6 KiB
C++
/* Copyright (c) 2015, 2017, Oracle and/or its affiliates. All rights reserved.
|
|
|
|
This program is free software; you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License, version 2.0,
|
|
as published by the Free Software Foundation.
|
|
|
|
This program is also distributed with certain software (including
|
|
but not limited to OpenSSL) that is licensed under separate terms,
|
|
as designated in a particular file or component or in included license
|
|
documentation. The authors of MySQL hereby grant you an additional
|
|
permission to link the program and your derivative works with the
|
|
separately licensed software that they have included with MySQL.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License, version 2.0, for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program; if not, write to the Free Software
|
|
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
|
|
|
|
#ifndef DD_CACHE__ELEMENT_MAP_INCLUDED
|
|
#define DD_CACHE__ELEMENT_MAP_INCLUDED
|
|
|
|
#include <cstddef> // size_t
|
|
#include <map> // std::map
|
|
#include <set> // std::set
|
|
|
|
#include "my_dbug.h"
|
|
#include "sql/malloc_allocator.h" // Malloc_allocator.
|
|
|
|
namespace dd {
|
|
namespace cache {
|
|
|
|
/**
|
|
Implementation of a map between a key type and an element type.
|
|
|
|
The map supports storing associations between instances of the key
|
|
type K and pointers to the element type E. Additionally, the map provides
|
|
support for registering keys that have been searched for in the map
|
|
without being present. This allows registering a cache miss to avoid
|
|
situations where several similar cache misses are handled simultaneously.
|
|
Instead, only the first cache miss needs to be processed, while the
|
|
subsequent ones can just wait for the first one to complete.
|
|
|
|
There are no expectations as far as the element type E is concerned.
|
|
Tracking object usage, memory management, loading and evicting elements,
|
|
locking and synchronization, as well as registering cache misses are all
|
|
issues that are handled by users of this interface.
|
|
|
|
Basic assumptions regarding correct usage is implemented in terms of
|
|
asserts to verify that, e.g., a key does not already exist in the map
|
|
when it is added. There is, however, no assumptions regarding the
|
|
relationship between the set of missed keys and the state of the map.
|
|
|
|
There is support for representing missed keys, but the usage of this
|
|
feature is left to the outer layer; e.g., this class does not assert
|
|
that an element has been registered as missing before it is added to
|
|
the map.
|
|
|
|
@note The element pointer in a key/value pair may not be NULL.
|
|
|
|
@tparam K Key type.
|
|
@tparam E Element type (a Cache_element wrapping some dictionary
|
|
object type).
|
|
*/
|
|
|
|
template <typename K, typename E>
|
|
class Element_map {
|
|
public:
|
|
typedef std::map<K, E *, std::less<K>,
|
|
Malloc_allocator<std::pair<const K, E *>>>
|
|
Element_map_type; // Real map type.
|
|
typedef typename Element_map_type::const_iterator
|
|
Const_iterator; // Const iterator type.
|
|
typedef typename Element_map_type::iterator Iterator; // Iterator type.
|
|
|
|
private:
|
|
Element_map_type m_map; // The real map instance.
|
|
std::set<K, std::less<K>,
|
|
Malloc_allocator<K>>
|
|
m_missed; // Cache misses being handled.
|
|
|
|
public:
|
|
Element_map()
|
|
: m_map(std::less<K>(),
|
|
Malloc_allocator<std::pair<const K, E *>>(PSI_INSTRUMENT_ME)),
|
|
m_missed(std::less<K>(), Malloc_allocator<K>(PSI_INSTRUMENT_ME)) {
|
|
} /* purecov: tested */
|
|
|
|
/**
|
|
Get an iterator to the beginning of the map.
|
|
|
|
Const and non-const variants.
|
|
|
|
@return Iterator to the beginning of the map.
|
|
*/
|
|
|
|
/* purecov: begin inspected */
|
|
Const_iterator begin() const { return m_map.begin(); }
|
|
/* purecov: end */
|
|
|
|
Iterator begin() { return m_map.begin(); }
|
|
|
|
/**
|
|
Get an iterator to one past the end of the map.
|
|
|
|
Const and non-const variants.
|
|
|
|
@return Iterator to one past the end of the map.
|
|
*/
|
|
|
|
/* purecov: begin inspected */
|
|
Const_iterator end() const { return m_map.end(); }
|
|
/* purecov: end */
|
|
|
|
Iterator end() { return m_map.end(); }
|
|
|
|
/**
|
|
Return the number of elements in the map.
|
|
|
|
@return Number of elements in the map.
|
|
*/
|
|
|
|
size_t size() const { return m_map.size(); }
|
|
|
|
/**
|
|
Check if the given key is present in the map.
|
|
|
|
If the key is present in the map, return true, otherwise false.
|
|
|
|
@param key The key to look for.
|
|
|
|
@return true if present, otherwise false.
|
|
*/
|
|
|
|
bool is_present(const K &key) const { return m_map.find(key) != m_map.end(); }
|
|
|
|
/**
|
|
Get the element associated with the given key.
|
|
|
|
If the element is present in the map, return a pointer to it. If the
|
|
element is not present, return NULL as the element pointer.
|
|
|
|
@param key The key to use for looking up the element.
|
|
@param [out] element The element associated with the key (if present),
|
|
or NULL (if not present).
|
|
*/
|
|
|
|
void get(const K &key, E **element) const {
|
|
DBUG_ASSERT(element);
|
|
typename Element_map_type::const_iterator it = m_map.find(key);
|
|
if (it == m_map.end())
|
|
*element = NULL;
|
|
else {
|
|
DBUG_ASSERT(it->second);
|
|
*element = it->second;
|
|
}
|
|
}
|
|
|
|
/**
|
|
Put the element into the map and associate it with the given key.
|
|
|
|
The element may not be NULL, and the key may not be already present.
|
|
|
|
@param key The key to be associated with the element.
|
|
@param element The element to be associated with the key.
|
|
*/
|
|
|
|
void put(const K &key, E *element) {
|
|
DBUG_ASSERT(element);
|
|
DBUG_ASSERT(m_map.find(key) == m_map.end());
|
|
m_map.insert(typename Element_map_type::value_type(key, element));
|
|
}
|
|
|
|
/**
|
|
Remove an element from the map.
|
|
|
|
The key/value pair, as indicated by the key, is removed from the map.
|
|
The element being pointed to is not deleted. The key must be present in
|
|
the map.
|
|
|
|
@param key The key to be removed.
|
|
*/
|
|
|
|
void remove(const K &key) {
|
|
DBUG_ASSERT(m_map.find(key) != m_map.end());
|
|
m_map.erase(key);
|
|
}
|
|
|
|
/**
|
|
Check if the given key has been missed in the cache.
|
|
|
|
@param key Key representing element to check for recent cache miss.
|
|
@return true if the element has been missed, otherwise false.
|
|
*/
|
|
|
|
bool is_missed(const K &key) const {
|
|
return m_missed.find(key) != m_missed.end();
|
|
}
|
|
|
|
/**
|
|
Register the given key as being missed in the cache.
|
|
|
|
The key cannot already be reported as missing.
|
|
|
|
@param key Key representing element missed in the cache.
|
|
*/
|
|
|
|
void set_missed(const K &key) {
|
|
DBUG_ASSERT(m_missed.find(key) == m_missed.end());
|
|
m_missed.insert(key);
|
|
}
|
|
|
|
/**
|
|
Register that the miss of a key has been handled.
|
|
|
|
The key must have been reported as missing.
|
|
|
|
@param key Key representing element previously missed in the cache.
|
|
*/
|
|
|
|
void set_miss_handled(const K &key) {
|
|
DBUG_ASSERT(m_missed.find(key) != m_missed.end());
|
|
m_missed.erase(key);
|
|
}
|
|
|
|
/**
|
|
Debug dump of the element map to stderr.
|
|
|
|
Iterates over all elements and dumps debug information for each
|
|
of them.
|
|
*/
|
|
|
|
/* purecov: begin inspected */
|
|
void dump() const {
|
|
#ifndef DBUG_OFF
|
|
Const_iterator it;
|
|
for (it = m_map.begin(); it != m_map.end(); it++) it->second->dump();
|
|
#endif
|
|
}
|
|
/* purecov: end */
|
|
};
|
|
|
|
} // namespace cache
|
|
} // namespace dd
|
|
|
|
#endif // DD_CACHE__ELEMENT_MAP_INCLUDED
|