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188 lines
6.0 KiB
188 lines
6.0 KiB
/* Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License, version 2.0,
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as published by the Free Software Foundation.
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This program is also distributed with certain software (including
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but not limited to OpenSSL) that is licensed under separate terms,
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as designated in a particular file or component or in included license
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documentation. The authors of MySQL hereby grant you an additional
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permission to link the program and your derivative works with the
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separately licensed software that they have included with MySQL.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License, version 2.0, for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
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#ifndef MDL_CONTEXT_BACKUP_H
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#define MDL_CONTEXT_BACKUP_H
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#include <cstring>
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#include <map>
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#include <memory>
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#include "sql/malloc_allocator.h"
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#include "sql/mdl.h"
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/**
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Class which is used to store MDL locks associated with XA transactions
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in prepared state which clients have disconnected. These locks are not
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associated with any particular THD/thread. Later they will be retrieved
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by the thread which attempts to process the prepared XA transaction.
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This is singleton class. It contains map where each element represents
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MDL_context of disconnected prepared XA transaction and holds related
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metadata locks.
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*/
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class MDL_context_backup_manager {
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private:
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/**
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Key for uniquely identifying MDL_context in the MDL_context_backup map.
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*/
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typedef std::basic_string<uchar> MDL_context_backup_key;
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class MDL_context_backup;
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typedef std::map<
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MDL_context_backup_key, std::unique_ptr<MDL_context_backup>,
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std::less<MDL_context_backup_key>,
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Malloc_allocator<std::pair<const MDL_context_backup_key,
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std::unique_ptr<MDL_context_backup>>>>
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Element_map_type; // Real map type.
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/* Singleton. No explicit Objects */
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MDL_context_backup_manager(PSI_memory_key key);
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/* Singleton Object */
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static MDL_context_backup_manager *m_single;
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public:
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/* Not copyable. */
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MDL_context_backup_manager(const MDL_context_backup_manager &) = delete;
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/* Not assignable. */
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void operator=(const MDL_context_backup_manager &) = delete;
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/**
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Initialize member variables and singleton object
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*/
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static bool init();
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/**
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Return singleton object
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*/
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static MDL_context_backup_manager &instance();
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/**
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Cleanup and delete singleton object
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*/
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static void destroy();
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private:
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/**
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destroy mutex and clear backup map
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*/
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~MDL_context_backup_manager();
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static void init_psi_keys(void);
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public:
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/**
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Create backup from given MDL_context by cloning all transactional
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locks to backup context and adds to backup context manager collection.
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This method is used during user's session disconnect for storing MDL
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locks acquired by prepared XA transaction(s).
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This function does not set error codes beyond what is set by the
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functions it calls.
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@param[in] context MDL_context from which backup is created.
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@param[in] key Key to identity MDL_context
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@param[in] keylen Key Length
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@retval true Error, e.g. Fail to create backup object, fail
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to clone locks.
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@retval false Success or a backup already exist for this key.
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*/
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bool create_backup(const MDL_context *context, const uchar *key,
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const size_t keylen);
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/**
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Create backup MDL_context, process request on it and add to backup context
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manager collection. This method is called during server start up in order
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to acquire MDL locks held by prepared XA transactions existed before server
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shutdown.
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This function does not set error codes beyond what is set by the
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functions it calls.
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@param[in] mdl_requests Requests need to be processed and backed up.
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@param[in] key Key to identity MDL_context
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@param[in] keylen Key Length
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@retval true Error, e.g. Fail to create backup object, fail
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to clone locks.
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@retval false Success or a backup already exist for this key.
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*/
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bool create_backup(MDL_request_list *mdl_requests, const uchar *key,
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const size_t keylen);
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/**
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Restore locks from backup to given MDL_context.
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This function does not set error codes beyond what is set by the
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functions it calls.
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@param[out] mdl_context MDL_context to which backup is restored.
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@param[in] key Key to identity MDL_context
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@param[in] keylen Key Length
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@retval true Error, e.g. There is no element in the
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collection matching given key, fail
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to retore locks.
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@retval false Success
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*/
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bool restore_backup(MDL_context *mdl_context, const uchar *key,
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const size_t keylen);
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/**
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Delete backup context and release associated locks.
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@param[in] key Key to identity MDL_context
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@param[in] keylen Key Length
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*/
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void delete_backup(const uchar *key, const size_t keylen);
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private:
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// Collection for holding MDL_context_backup elements
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Element_map_type m_backup_map;
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// Mutex to protect m_backup_map
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mysql_mutex_t m_LOCK_mdl_context_backup;
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/**
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Check for presence of a record with specified key
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@param[in] key_obj Key to identity MDL_context
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@return true if there is a record for specified key, else false
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*/
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bool check_key_exist(const MDL_context_backup_key &key_obj);
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};
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#endif // MDL_CONTEXT_BACKUP_H
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