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MDEV-7964 - delete_dynamic() takes 0.12% in OLTP RO

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delete_dynamic() was called 9-11x per OLTP RO query + 3x per BEGIN/COMMIT.

3 calls were performed by LEX_MASTER_INFO. Added condition to call those only
for CHANGE MASTER.

1 call was performed by lock_table_names()/Hash_set/my_hash_free(). Hash_set was
supposed to be used for DDL and LOCK TABLES to gather database names, while it
was initialized/freed for DML too. In fact Hash_set didn't do any useful job
here. Hash_set was removed and MDL requests are now added directly to the list.

The rest 5-7 calls are done by optimizer, mostly by Explain_query and friends.
Since dynamic arrays are used in most cases, they can hardly be optimized.

my_hash_free() overhead dropped 0.02 -> out of radar.
delete_dynamic() overhead dropped 0.12 -> 0.04.
This commit is contained in:
Sergey Vojtovich
2015-04-16 18:38:26 +04:00
parent 7cfa803d8e
commit c4d2c4e844
3 changed files with 20 additions and 32 deletions
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37
sql/sql_base.cc
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@ -4174,12 +4174,6 @@ end:
DBUG_RETURN(error);
}
extern "C" uchar *schema_set_get_key(const TABLE_LIST *table, size_t *length,
my_bool not_used __attribute__((unused)))
{
*length= table->db_length;
return (uchar*) table->db;
}
/**
Acquire upgradable (SNW, SNRW) metadata locks on tables used by
@ -4217,7 +4211,6 @@ lock_table_names(THD *thd, const DDL_options_st &options,
MDL_request_list mdl_requests;
TABLE_LIST *table;
MDL_request global_request;
Hash_set<TABLE_LIST> schema_set(schema_set_get_key);
ulong org_lock_wait_timeout= lock_wait_timeout;
/* Check if we are using CREATE TABLE ... IF NOT EXISTS */
bool create_table;
@ -4243,9 +4236,17 @@ lock_table_names(THD *thd, const DDL_options_st &options,
DBUG_RETURN(true);
}
if (! (flags & MYSQL_OPEN_SKIP_SCOPED_MDL_LOCK) &&
schema_set.insert(table))
DBUG_RETURN(TRUE);
/* Scoped locks: Take intention exclusive locks on all involved schemas. */
if (!(flags & MYSQL_OPEN_SKIP_SCOPED_MDL_LOCK))
{
MDL_request *schema_request= new (thd->mem_root) MDL_request;
if (schema_request == NULL)
DBUG_RETURN(TRUE);
schema_request->init(MDL_key::SCHEMA, table->db, "",
MDL_INTENTION_EXCLUSIVE,
MDL_TRANSACTION);
mdl_requests.push_front(schema_request);
}
mdl_requests.push_front(&table->mdl_request);
}
@ -4259,22 +4260,6 @@ lock_table_names(THD *thd, const DDL_options_st &options,
if (!(flags & MYSQL_OPEN_SKIP_SCOPED_MDL_LOCK))
{
/*
Scoped locks: Take intention exclusive locks on all involved
schemas.
*/
Hash_set<TABLE_LIST>::Iterator it(schema_set);
while ((table= it++))
{
MDL_request *schema_request= new (thd->mem_root) MDL_request;
if (schema_request == NULL)
DBUG_RETURN(TRUE);
schema_request->init(MDL_key::SCHEMA, table->db, "",
MDL_INTENTION_EXCLUSIVE,
MDL_TRANSACTION);
mdl_requests.push_front(schema_request);
}
/*
Protect this statement against concurrent global read lock
by acquiring global intention exclusive lock with statement