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A minor change to MySQL's hash where calculation of hash can be done separately to avoid doing it under contended mutex locks

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This commit is contained in:
Mikael Ronstrom 2009-10-09 14:22:22 +02:00
parent ee696e4163
commit d3540b216f
3 changed files with 43 additions and 4 deletions
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9
include/hash.h
View file

@ -45,6 +45,7 @@ extern "C" {
#define hash_element my_hash_element
#define hash_search my_hash_search
#define hash_first my_hash_first
#define hash_first_from_hash_value my_hash_first_from_hash_value
#define hash_next my_hash_next
#define hash_insert my_hash_insert
#define hash_delete my_hash_delete
@ -94,8 +95,16 @@ void my_hash_free(HASH *tree);
void my_hash_reset(HASH *hash);
uchar *my_hash_element(HASH *hash, ulong idx);
uchar *my_hash_search(const HASH *info, const uchar *key, size_t length);
uchar *my_hash_search_using_hash_value(const HASH *info, uint hash_value,
const uchar *key, size_t length);
uint my_calc_hash(const HASH *info, const uchar *key, size_t length);
uchar *my_hash_first(const HASH *info, const uchar *key, size_t length,
HASH_SEARCH_STATE *state);
uchar *my_hash_first_from_hash_value(const HASH *info,
uint hash_value,
const uchar *key,
size_t length,
HASH_SEARCH_STATE *state);
uchar *my_hash_next(const HASH *info, const uchar *key, size_t length,
HASH_SEARCH_STATE *state);
my_bool my_hash_insert(HASH *info, const uchar *data);

29
mysys/hash.c
View file

@ -214,6 +214,20 @@ uchar* my_hash_search(const HASH *hash, const uchar *key, size_t length)
return my_hash_first(hash, key, length, &state);
}
uchar* my_hash_search_using_hash_value(const HASH *hash,
uint hash_value,
const uchar *key,
size_t length)
{
HASH_SEARCH_STATE state;
return my_hash_first_from_hash_value(hash, hash_value,
key, length, &state);
}
uint my_calc_hash(const HASH *hash, const uchar *key, size_t length)
{
return calc_hash(hash, key, length ? length : hash->key_length);
}
/*
Search after a record based on a key
@ -223,15 +237,26 @@ uchar* my_hash_search(const HASH *hash, const uchar *key, size_t length)
uchar* my_hash_first(const HASH *hash, const uchar *key, size_t length,
HASH_SEARCH_STATE *current_record)
{
return my_hash_first_from_hash_value(hash,
calc_hash(hash, key, length ? length : hash->key_length),
key, length, current_record);
}
uchar* my_hash_first_from_hash_value(const HASH *hash,
uint hash_value,
const uchar *key,
size_t length,
HASH_SEARCH_STATE *current_record)
{
HASH_LINK *pos;
uint flag,idx;
DBUG_ENTER("my_hash_first");
DBUG_ENTER("my_hash_first_from_hash_value");
flag=1;
if (hash->records)
{
idx= my_hash_mask(calc_hash(hash, key, length ? length : hash->key_length),
idx= my_hash_mask(hash_value,
hash->blength, hash->records);
do
{

9
sql/sql_base.cc
View file

@ -2513,6 +2513,7 @@ TABLE *open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
char key[MAX_DBKEY_LENGTH];
uint key_length;
char *alias= table_list->alias;
uint hash_value;
HASH_SEARCH_STATE state;
DBUG_ENTER("open_table");
@ -2702,6 +2703,7 @@ TABLE *open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
on disk.
*/
hash_value= my_calc_hash(&open_cache, (uchar*) key, key_length);
VOID(pthread_mutex_lock(&LOCK_open));
/*
@ -2744,8 +2746,11 @@ TABLE *open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
an implicit "pending locks queue" - see
wait_for_locked_table_names for details.
*/
for (table= (TABLE*) hash_first(&open_cache, (uchar*) key, key_length,
&state);
for (table= (TABLE*) hash_first_from_hash_value(&open_cache,
hash_value,
(uchar*) key,
key_length,
&state);
table && table->in_use ;
table= (TABLE*) hash_next(&open_cache, (uchar*) key, key_length,
&state))