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312 lines
8.9 KiB
312 lines
8.9 KiB
/* Copyright (c) 2003, 2019, 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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Without limiting anything contained in the foregoing, this file,
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which is part of C Driver for MySQL (Connector/C), is also subject to the
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Universal FOSS Exception, version 1.0, a copy of which can be found at
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http://oss.oracle.com/licenses/universal-foss-exception.
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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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/**
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@file mysys/mf_keycaches.cc
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Handling of multiple key caches.
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The idea is to have a thread safe hash on the table name,
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with a default key cache value that is returned if the table name is not in
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the cache.
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*/
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#include <string.h>
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#include <sys/types.h>
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#include <string>
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#include "keycache.h"
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#include "m_ctype.h"
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#include "map_helpers.h"
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#include "my_dbug.h"
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#include "my_inttypes.h"
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#include "my_sys.h"
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#include "mysql/psi/mysql_rwlock.h"
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#include "mysql/service_mysql_alloc.h"
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#include "mysys/mysys_priv.h"
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#include "template_utils.h"
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using std::string;
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/*****************************************************************************
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General functions to handle SAFE_HASH objects.
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A SAFE_HASH object is used to store the hash, the lock and default value
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needed by the rest of the key cache code.
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This is a separate struct to make it easy to later reuse the code for other
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purposes
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All entries are linked in a list to allow us to traverse all elements
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and delete selected ones. (HASH doesn't allow any easy ways to do this).
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*****************************************************************************/
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/*
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Struct to store a key and pointer to object
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*/
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struct SAFE_HASH_ENTRY {
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char *key;
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uint length;
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uchar *data;
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SAFE_HASH_ENTRY *next, **prev;
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};
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struct SAFE_HASH {
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mysql_rwlock_t lock;
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malloc_unordered_map<string, unique_ptr_my_free<SAFE_HASH_ENTRY>> hash{
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key_memory_SAFE_HASH_ENTRY};
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uchar *default_value;
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SAFE_HASH_ENTRY *root;
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};
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/*
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Init a SAFE_HASH object
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SYNOPSIS
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safe_hash_init()
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hash safe_hash handler
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elements Expected max number of elements
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default_value default value
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NOTES
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In case of error we set hash->default_value to 0 to allow one to call
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safe_hash_free on an object that couldn't be initialized.
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RETURN
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0 ok
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1 error
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*/
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static bool safe_hash_init(SAFE_HASH *hash, uchar *default_value) {
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DBUG_TRACE;
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mysql_rwlock_init(key_SAFE_HASH_lock, &hash->lock);
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hash->default_value = default_value;
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hash->root = 0;
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return 0;
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}
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/*
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Free a SAFE_HASH object
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NOTES
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This is safe to call on any object that has been sent to safe_hash_init()
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*/
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static void safe_hash_free(SAFE_HASH *hash) {
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/*
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Test if safe_hash_init succeeded. This will also guard us against multiple
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free calls.
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*/
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if (hash->default_value) {
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hash->hash.clear();
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mysql_rwlock_destroy(&hash->lock);
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hash->default_value = 0;
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}
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}
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/*
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Return the value stored for a key or default value if no key
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*/
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static uchar *safe_hash_search(SAFE_HASH *hash, const uchar *key, uint length) {
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uchar *result;
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DBUG_TRACE;
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mysql_rwlock_rdlock(&hash->lock);
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auto it = hash->hash.find(string(pointer_cast<const char *>(key), length));
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if (it == hash->hash.end())
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result = hash->default_value;
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else
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result = it->second->data;
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mysql_rwlock_unlock(&hash->lock);
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DBUG_PRINT("exit", ("data: %p", result));
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return result;
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}
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/*
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Associate a key with some data
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SYONOPSIS
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safe_hash_set()
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hash Hash handle
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key key (path to table etc..)
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length Length of key
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data data to to associate with the data
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NOTES
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This can be used both to insert a new entry and change an existing
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entry.
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If one associates a key with the default key cache, the key is deleted
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RETURN
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0 ok
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1 error (Can only be EOM). In this case my_message() is called.
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*/
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static bool safe_hash_set(SAFE_HASH *hash, const uchar *key, uint length,
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uchar *data) {
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SAFE_HASH_ENTRY *entry;
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bool error = 0;
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DBUG_TRACE;
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DBUG_PRINT("enter", ("key: %.*s data: %p", length, key, data));
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string key_str(pointer_cast<const char *>(key), length);
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mysql_rwlock_wrlock(&hash->lock);
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entry = find_or_nullptr(hash->hash, key_str);
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if (data == hash->default_value) {
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/*
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The key is to be associated with the default entry. In this case
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we can just delete the entry (if it existed) from the hash as a
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search will return the default entry
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*/
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if (!entry) /* nothing to do */
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goto end;
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/* unlink entry from list */
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if ((*entry->prev = entry->next)) entry->next->prev = entry->prev;
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hash->hash.erase(key_str);
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goto end;
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}
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if (entry) {
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/* Entry existed; Just change the pointer to point at the new data */
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entry->data = data;
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} else {
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if (!(entry = (SAFE_HASH_ENTRY *)my_malloc(key_memory_SAFE_HASH_ENTRY,
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sizeof(*entry) + length,
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MYF(MY_WME)))) {
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error = 1;
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goto end;
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}
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entry->key = (char *)(entry + 1);
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memcpy(entry->key, key, length);
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entry->length = length;
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entry->data = data;
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/* Link entry to list */
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if ((entry->next = hash->root)) entry->next->prev = &entry->next;
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entry->prev = &hash->root;
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hash->root = entry;
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hash->hash.emplace(
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string(pointer_cast<const char *>(entry->key), entry->length),
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unique_ptr_my_free<SAFE_HASH_ENTRY>(entry));
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}
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end:
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mysql_rwlock_unlock(&hash->lock);
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return error;
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}
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/*
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Change all entres with one data value to another data value
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SYONOPSIS
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safe_hash_change()
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hash Hash handle
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old_data Old data
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new_data Change all 'old_data' to this
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NOTES
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We use the linked list to traverse all elements in the hash as
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this allows us to delete elements in the case where 'new_data' is the
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default value.
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*/
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static void safe_hash_change(SAFE_HASH *hash, uchar *old_data,
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uchar *new_data) {
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SAFE_HASH_ENTRY *entry, *next;
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DBUG_TRACE;
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mysql_rwlock_wrlock(&hash->lock);
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for (entry = hash->root; entry; entry = next) {
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next = entry->next;
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if (entry->data == old_data) {
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if (new_data == hash->default_value) {
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if ((*entry->prev = entry->next)) entry->next->prev = entry->prev;
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hash->hash.erase(string(entry->key, entry->length));
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} else
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entry->data = new_data;
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}
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}
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mysql_rwlock_unlock(&hash->lock);
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}
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/*****************************************************************************
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Functions to handle the key cache objects
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*****************************************************************************/
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/* Variable to store all key cache objects */
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static SAFE_HASH key_cache_hash;
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bool multi_keycache_init(void) {
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return safe_hash_init(&key_cache_hash, (uchar *)dflt_key_cache);
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}
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void multi_keycache_free(void) { safe_hash_free(&key_cache_hash); }
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/*
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Get a key cache to be used for a specific table.
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SYNOPSIS
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multi_key_cache_search()
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key key to find (usually table path)
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uint length Length of key.
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NOTES
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This function is coded in such a way that we will return the
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default key cache even if one never called multi_keycache_init.
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This will ensure that it works with old MyISAM clients.
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RETURN
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key cache to use
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*/
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KEY_CACHE *multi_key_cache_search(uchar *key, uint length) {
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if (key_cache_hash.hash.empty()) return dflt_key_cache;
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return (KEY_CACHE *)safe_hash_search(&key_cache_hash, key, length);
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}
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/*
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Assosiate a key cache with a key
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SYONOPSIS
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multi_key_cache_set()
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key key (path to table etc..)
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length Length of key
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key_cache cache to assococite with the table
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NOTES
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This can be used both to insert a new entry and change an existing
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entry
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*/
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bool multi_key_cache_set(const uchar *key, uint length, KEY_CACHE *key_cache) {
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return safe_hash_set(&key_cache_hash, key, length, (uchar *)key_cache);
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}
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void multi_key_cache_change(KEY_CACHE *old_data, KEY_CACHE *new_data) {
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safe_hash_change(&key_cache_hash, (uchar *)old_data, (uchar *)new_data);
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}
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