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A 5.5 version of the fix for Bug #54360 "Deadlock DROP/ALTER/CREATE

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DATABASE with open HANDLER"

Remove LOCK_create_db, database name locks, and use metadata locks instead.
This exposes CREATE/DROP/ALTER DATABASE statements to the graph-based
deadlock detector in MDL, and paves the way for a safe, deadlock-free
implementation of RENAME DATABASE.

Database DDL statements will now take exclusive metadata locks on
the database name, while table/view/routine DDL statements take
intention exclusive locks on the database name. This prevents race
conditions between database DDL and table/view/routine DDL.
(e.g. DROP DATABASE with concurrent CREATE/ALTER/DROP TABLE)

By adding database name locks, this patch implements
WL#4450 "DDL locking: CREATE/DROP DATABASE must use database locks" and
WL#4985 "DDL locking: namespace/hierarchical locks".

The patch also changes code to use init_one_table() where appropriate.
The new lock_table_names() function requires TABLE_LIST::db_length to
be set correctly, and this is taken care of by init_one_table().

This patch also adds a simple template to help work with 
the mysys HASH data structure.

Most of the patch was written by Konstantin Osipov.
This commit is contained in:
Jon Olav Hauglid
2010-07-01 15:53:46 +02:00
parent 34e409fafa
commit 41a3dfe490
28 changed files with 1300 additions and 652 deletions
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49
sql/sql_table.cc
View File

@@ -22,17 +22,17 @@
#include "sql_rename.h" // do_rename
#include "sql_parse.h" // test_if_data_home_dir
#include "sql_cache.h" // query_cache_*
#include "sql_base.h" // open_temporary_table
#include "lock.h" // wait_if_global_read_lock, lock_table_names,
#include "sql_base.h" // open_temporary_table, lock_table_names
#include "lock.h" // wait_if_global_read_lock
// start_waiting_global_read_lock,
// unlock_table_names, mysql_unlock_tables
// mysql_unlock_tables
#include "strfunc.h" // find_type2, find_set
#include "sql_view.h" // view_checksum
#include "sql_truncate.h" // regenerate_locked_table
#include "sql_partition.h" // mem_alloc_error,
// generate_partition_syntax,
// partition_info
#include "sql_db.h" // load_db_opt_by_name, lock_db_cache, creating_database
#include "sql_db.h" // load_db_opt_by_name
#include "sql_time.h" // make_truncated_value_warning
#include "records.h" // init_read_record, end_read_record
#include "filesort.h" // filesort_free_buffers
@@ -58,8 +58,6 @@
#include <io.h>
#endif
int creating_table= 0; // How many mysql_create_table are running
const char *primary_key_name="PRIMARY";
static bool check_if_keyname_exists(const char *name,KEY *start, KEY *end);
@@ -1954,7 +1952,8 @@ int mysql_rm_table_part2(THD *thd, TABLE_LIST *tables, bool if_exists,
{
if (!thd->locked_tables_mode)
{
if (lock_table_names(thd, tables))
if (lock_table_names(thd, tables, NULL, thd->variables.lock_wait_timeout,
MYSQL_OPEN_SKIP_TEMPORARY))
DBUG_RETURN(1);
mysql_mutex_lock(&LOCK_open);
for (table= tables; table; table= table->next_local)
@@ -2296,7 +2295,7 @@ err:
leaving LOCK TABLES mode if we have dropped only temporary tables.
*/
if (! thd->locked_tables_mode)
unlock_table_names(thd);
thd->mdl_context.release_transactional_locks();
else
{
if (thd->lock && thd->lock->table_count == 0 && non_temp_tables_count > 0)
@@ -4226,24 +4225,6 @@ bool mysql_create_table(THD *thd, TABLE_LIST *create_table,
bool result;
DBUG_ENTER("mysql_create_table");
/* Wait for any database locks */
mysql_mutex_lock(&LOCK_lock_db);
while (!thd->killed &&
my_hash_search(&lock_db_cache, (uchar*)create_table->db,
create_table->db_length))
{
wait_for_condition(thd, &LOCK_lock_db, &COND_refresh);
mysql_mutex_lock(&LOCK_lock_db);
}
if (thd->killed)
{
mysql_mutex_unlock(&LOCK_lock_db);
DBUG_RETURN(TRUE);
}
creating_table++;
mysql_mutex_unlock(&LOCK_lock_db);
/*
Open or obtain an exclusive metadata lock on table being created.
*/
@@ -4282,10 +4263,6 @@ bool mysql_create_table(THD *thd, TABLE_LIST *create_table,
}
unlock:
mysql_mutex_lock(&LOCK_lock_db);
if (!--creating_table && creating_database)
mysql_cond_signal(&COND_refresh);
mysql_mutex_unlock(&LOCK_lock_db);
DBUG_RETURN(result);
}
@@ -4458,8 +4435,6 @@ static int prepare_for_repair(THD *thd, TABLE_LIST *table_list,
{
char key[MAX_DBKEY_LENGTH];
uint key_length;
MDL_request mdl_global_request;
MDL_request_list mdl_requests;
/*
If the table didn't exist, we have a shared metadata lock
on it that is left from mysql_admin_table()'s attempt to
@@ -4479,12 +4454,9 @@ static int prepare_for_repair(THD *thd, TABLE_LIST *table_list,
table_list->db, table_list->table_name,
MDL_EXCLUSIVE);
mdl_global_request.init(MDL_key::GLOBAL, "", "", MDL_INTENTION_EXCLUSIVE);
mdl_requests.push_front(&table_list->mdl_request);
mdl_requests.push_front(&mdl_global_request);
if (thd->mdl_context.acquire_locks(&mdl_requests,
thd->variables.lock_wait_timeout))
if (lock_table_names(thd, table_list, table_list->next_global,
thd->variables.lock_wait_timeout,
MYSQL_OPEN_SKIP_TEMPORARY))
DBUG_RETURN(0);
has_mdl_lock= TRUE;
@@ -6577,6 +6549,7 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
Alter_table_prelocking_strategy alter_prelocking_strategy(alter_info);
DEBUG_SYNC(thd, "alter_table_before_open_tables");
error= open_and_lock_tables(thd, table_list, FALSE, 0,
&alter_prelocking_strategy);