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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
sql/sql_base.cc
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@ -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))