From 354bb40e75d94466e91fe6960523612c9d17ccfb Mon Sep 17 00:00:00 2001 From: Karen Arutyunov Date: Thu, 2 Nov 2017 23:11:29 +0300 Subject: Add implementation --- mysql/mysys/mf_keycaches.c | 363 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 363 insertions(+) create mode 100644 mysql/mysys/mf_keycaches.c (limited to 'mysql/mysys/mf_keycaches.c') diff --git a/mysql/mysys/mf_keycaches.c b/mysql/mysys/mf_keycaches.c new file mode 100644 index 0000000..8622105 --- /dev/null +++ b/mysql/mysys/mf_keycaches.c @@ -0,0 +1,363 @@ +/* Copyright (c) 2003, 2016, 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 as published by + the Free Software Foundation; version 2 of the License. + + 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 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 */ + +/* + Handling of multiple key caches + + The idea is to have a thread safe hash on the table name, + with a default key cache value that is returned if the table name is not in + the cache. +*/ + +#include "mysys_priv.h" +#include +#include +#include + +/***************************************************************************** + General functions to handle SAFE_HASH objects. + + A SAFE_HASH object is used to store the hash, the lock and default value + needed by the rest of the key cache code. + This is a separate struct to make it easy to later reuse the code for other + purposes + + All entries are linked in a list to allow us to traverse all elements + and delete selected ones. (HASH doesn't allow any easy ways to do this). +*****************************************************************************/ + +/* + Struct to store a key and pointer to object +*/ + +typedef struct st_safe_hash_entry +{ + uchar *key; + uint length; + uchar *data; + struct st_safe_hash_entry *next, **prev; +} SAFE_HASH_ENTRY; + + +typedef struct st_safe_hash_with_default +{ + mysql_rwlock_t lock; + HASH hash; + uchar *default_value; + SAFE_HASH_ENTRY *root; +} SAFE_HASH; + + +/* + Free a SAFE_HASH_ENTRY + + This function is called by the hash object on delete +*/ + +static void safe_hash_entry_free(SAFE_HASH_ENTRY *entry) +{ + DBUG_ENTER("free_assign_entry"); + my_free(entry); + DBUG_VOID_RETURN; +} + + +/* Get key and length for a SAFE_HASH_ENTRY */ + +static uchar *safe_hash_entry_get(SAFE_HASH_ENTRY *entry, size_t *length, + my_bool not_used MY_ATTRIBUTE((unused))) +{ + *length=entry->length; + return (uchar*) entry->key; +} + + +/* + Init a SAFE_HASH object + + SYNOPSIS + safe_hash_init() + hash safe_hash handler + elements Expected max number of elements + default_value default value + + NOTES + In case of error we set hash->default_value to 0 to allow one to call + safe_hash_free on an object that couldn't be initialized. + + RETURN + 0 ok + 1 error +*/ + +static my_bool safe_hash_init(SAFE_HASH *hash, uint elements, + uchar *default_value) +{ + DBUG_ENTER("safe_hash"); + if (my_hash_init(&hash->hash, &my_charset_bin, elements, + 0, 0, (my_hash_get_key) safe_hash_entry_get, + (void (*)(void*)) safe_hash_entry_free, 0, + key_memory_SAFE_HASH_ENTRY)) + { + hash->default_value= 0; + DBUG_RETURN(1); + } + mysql_rwlock_init(key_SAFE_HASH_lock, &hash->lock); + hash->default_value= default_value; + hash->root= 0; + DBUG_RETURN(0); +} + + +/* + Free a SAFE_HASH object + + NOTES + This is safe to call on any object that has been sent to safe_hash_init() +*/ + +static void safe_hash_free(SAFE_HASH *hash) +{ + /* + Test if safe_hash_init succeeded. This will also guard us against multiple + free calls. + */ + if (hash->default_value) + { + my_hash_free(&hash->hash); + mysql_rwlock_destroy(&hash->lock); + hash->default_value=0; + } +} + +/* + Return the value stored for a key or default value if no key +*/ + +static uchar *safe_hash_search(SAFE_HASH *hash, const uchar *key, uint length) +{ + uchar *result; + DBUG_ENTER("safe_hash_search"); + mysql_rwlock_rdlock(&hash->lock); + result= my_hash_search(&hash->hash, key, length); + mysql_rwlock_unlock(&hash->lock); + if (!result) + result= hash->default_value; + else + result= ((SAFE_HASH_ENTRY*) result)->data; + DBUG_PRINT("exit",("data: 0x%lx", (long) result)); + DBUG_RETURN(result); +} + + +/* + Associate a key with some data + + SYONOPSIS + safe_hash_set() + hash Hash handle + key key (path to table etc..) + length Length of key + data data to to associate with the data + + NOTES + This can be used both to insert a new entry and change an existing + entry. + If one associates a key with the default key cache, the key is deleted + + RETURN + 0 ok + 1 error (Can only be EOM). In this case my_message() is called. +*/ + +static my_bool safe_hash_set(SAFE_HASH *hash, const uchar *key, uint length, + uchar *data) +{ + SAFE_HASH_ENTRY *entry; + my_bool error= 0; + DBUG_ENTER("safe_hash_set"); + DBUG_PRINT("enter",("key: %.*s data: 0x%lx", length, key, (long) data)); + + mysql_rwlock_wrlock(&hash->lock); + entry= (SAFE_HASH_ENTRY*) my_hash_search(&hash->hash, key, length); + + if (data == hash->default_value) + { + /* + The key is to be associated with the default entry. In this case + we can just delete the entry (if it existed) from the hash as a + search will return the default entry + */ + if (!entry) /* nothing to do */ + goto end; + /* unlink entry from list */ + if ((*entry->prev= entry->next)) + entry->next->prev= entry->prev; + my_hash_delete(&hash->hash, (uchar*) entry); + goto end; + } + if (entry) + { + /* Entry existed; Just change the pointer to point at the new data */ + entry->data= data; + } + else + { + if (!(entry= (SAFE_HASH_ENTRY *) my_malloc(key_memory_SAFE_HASH_ENTRY, + sizeof(*entry) + length, + MYF(MY_WME)))) + { + error= 1; + goto end; + } + entry->key= (uchar*) (entry +1); + memcpy((char*) entry->key, (char*) key, length); + entry->length= length; + entry->data= data; + /* Link entry to list */ + if ((entry->next= hash->root)) + entry->next->prev= &entry->next; + entry->prev= &hash->root; + hash->root= entry; + if (my_hash_insert(&hash->hash, (uchar*) entry)) + { + /* This can only happen if hash got out of memory */ + my_free(entry); + error= 1; + goto end; + } + } + +end: + mysql_rwlock_unlock(&hash->lock); + DBUG_RETURN(error); +} + + +/* + Change all entres with one data value to another data value + + SYONOPSIS + safe_hash_change() + hash Hash handle + old_data Old data + new_data Change all 'old_data' to this + + NOTES + We use the linked list to traverse all elements in the hash as + this allows us to delete elements in the case where 'new_data' is the + default value. +*/ + +static void safe_hash_change(SAFE_HASH *hash, uchar *old_data, uchar *new_data) +{ + SAFE_HASH_ENTRY *entry, *next; + DBUG_ENTER("safe_hash_set"); + + mysql_rwlock_wrlock(&hash->lock); + + for (entry= hash->root ; entry ; entry= next) + { + next= entry->next; + if (entry->data == old_data) + { + if (new_data == hash->default_value) + { + if ((*entry->prev= entry->next)) + entry->next->prev= entry->prev; + my_hash_delete(&hash->hash, (uchar*) entry); + } + else + entry->data= new_data; + } + } + + mysql_rwlock_unlock(&hash->lock); + DBUG_VOID_RETURN; +} + + +/***************************************************************************** + Functions to handle the key cache objects +*****************************************************************************/ + +/* Variable to store all key cache objects */ +static SAFE_HASH key_cache_hash; + + +my_bool multi_keycache_init(void) +{ + return safe_hash_init(&key_cache_hash, 16, (uchar*) dflt_key_cache); +} + + +void multi_keycache_free(void) +{ + safe_hash_free(&key_cache_hash); +} + +/* + Get a key cache to be used for a specific table. + + SYNOPSIS + multi_key_cache_search() + key key to find (usually table path) + uint length Length of key. + + NOTES + This function is coded in such a way that we will return the + default key cache even if one never called multi_keycache_init. + This will ensure that it works with old MyISAM clients. + + RETURN + key cache to use +*/ + +KEY_CACHE *multi_key_cache_search(uchar *key, uint length) +{ + if (!key_cache_hash.hash.records) + return dflt_key_cache; + return (KEY_CACHE*) safe_hash_search(&key_cache_hash, key, length); +} + + +/* + Assosiate a key cache with a key + + + SYONOPSIS + multi_key_cache_set() + key key (path to table etc..) + length Length of key + key_cache cache to assococite with the table + + NOTES + This can be used both to insert a new entry and change an existing + entry +*/ + + +my_bool multi_key_cache_set(const uchar *key, uint length, + KEY_CACHE *key_cache) +{ + return safe_hash_set(&key_cache_hash, key, length, (uchar*) key_cache); +} + + +void multi_key_cache_change(KEY_CACHE *old_data, + KEY_CACHE *new_data) +{ + safe_hash_change(&key_cache_hash, (uchar*) old_data, (uchar*) new_data); +} -- cgit v1.1