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-rw-r--r--mysys/mf_keycaches.c359
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diff --git a/mysys/mf_keycaches.c b/mysys/mf_keycaches.c
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+/* Copyright (C) 2003 MySQL AB
+
+ 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; either version 2 of the License, or
+ (at your option) any later version.
+
+ 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 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 <hash.h>
+#include <m_string.h>
+
+/*****************************************************************************
+ General functions to handle SAFE_HASH objects.
+
+ A SAFE_HASH object is used to store the hash, the mutex 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
+{
+ byte *key;
+ uint length;
+ byte *data;
+ struct st_safe_hash_entry *next, **prev;
+} SAFE_HASH_ENTRY;
+
+
+typedef struct st_safe_hash_with_default
+{
+#ifdef THREAD
+ rw_lock_t mutex;
+#endif
+ HASH hash;
+ byte *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((gptr) entry, MYF(0));
+ DBUG_VOID_RETURN;
+}
+
+
+/* Get key and length for a SAFE_HASH_ENTRY */
+
+static byte *safe_hash_entry_get(SAFE_HASH_ENTRY *entry, uint *length,
+ my_bool not_used __attribute__((unused)))
+{
+ *length=entry->length;
+ return (byte*) 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,
+ byte *default_value)
+{
+ DBUG_ENTER("safe_hash");
+ if (hash_init(&hash->hash, &my_charset_bin, elements,
+ 0, 0, (hash_get_key) safe_hash_entry_get,
+ (void (*)(void*)) safe_hash_entry_free, 0))
+ {
+ hash->default_value= 0;
+ DBUG_RETURN(1);
+ }
+ my_rwlock_init(&hash->mutex, 0);
+ 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)
+ {
+ hash_free(&hash->hash);
+ rwlock_destroy(&hash->mutex);
+ hash->default_value=0;
+ }
+}
+
+/*
+ Return the value stored for a key or default value if no key
+*/
+
+static byte *safe_hash_search(SAFE_HASH *hash, const byte *key, uint length)
+{
+ byte *result;
+ DBUG_ENTER("safe_hash_search");
+ rw_rdlock(&hash->mutex);
+ result= hash_search(&hash->hash, key, length);
+ rw_unlock(&hash->mutex);
+ if (!result)
+ result= hash->default_value;
+ else
+ result= ((SAFE_HASH_ENTRY*) result)->data;
+ DBUG_PRINT("exit",("data: %lx", 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 byte *key, uint length,
+ byte *data)
+{
+ SAFE_HASH_ENTRY *entry;
+ my_bool error= 0;
+ DBUG_ENTER("safe_hash_set");
+ DBUG_PRINT("enter",("key: %.*s data: %lx", length, key, data));
+
+ rw_wrlock(&hash->mutex);
+ entry= (SAFE_HASH_ENTRY*) 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;
+ hash_delete(&hash->hash, (byte*) 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(sizeof(*entry) + length,
+ MYF(MY_WME))))
+ {
+ error= 1;
+ goto end;
+ }
+ entry->key= (byte*) (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, (byte*) entry))
+ {
+ /* This can only happen if hash got out of memory */
+ my_delete((char*) entry, MYF(0));
+ error= 1;
+ goto end;
+ }
+ }
+
+end:
+ rw_unlock(&hash->mutex);
+ 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, byte *old_data, byte *new_data)
+{
+ SAFE_HASH_ENTRY *entry, *next;
+ DBUG_ENTER("safe_hash_set");
+
+ rw_wrlock(&hash->mutex);
+
+ for (entry= hash->root ; entry ; entry= next)
+ {
+ next= entry->next;
+ if (entry->data == old_data)
+ {
+ if (new_data == hash->default_value)
+ hash_delete(&hash->hash, (byte*) entry);
+ else
+ entry->data= new_data;
+ }
+ }
+
+ rw_unlock(&hash->mutex);
+ 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, (byte*) dflt_keycache);
+}
+
+
+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_get()
+ 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_HANDLE *multi_key_cache_search(byte *key, uint length)
+{
+ if (!key_cache_hash.hash.records)
+ return dflt_keycache;
+ return (KEY_CACHE_HANDLE*) 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 byte *key, uint length,
+ KEY_CACHE_HANDLE *key_cache)
+{
+ return safe_hash_set(&key_cache_hash, key, length, (byte*) key_cache);
+}
+
+
+void multi_key_cache_change(KEY_CACHE_HANDLE *old_data,
+ KEY_CACHE_HANDLE *new_data)
+{
+ safe_hash_change(&key_cache_hash, (byte*) old_data, (byte*) new_data);
+}
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