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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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42
sql/sql_truncate.cc
View File

@ -242,9 +242,10 @@ static bool open_and_lock_table_for_truncate(THD *thd, TABLE_LIST *table_ref,
MDL_ticket **ticket_downgrade)
{
TABLE *table= NULL;
MDL_ticket *mdl_ticket= NULL;
DBUG_ENTER("open_and_lock_table_for_truncate");
DBUG_ASSERT(table_ref->lock_type == TL_WRITE);
DBUG_ASSERT(table_ref->mdl_request.type == MDL_SHARED_NO_READ_WRITE);
/*
Before doing anything else, acquire a metadata lock on the table,
or ensure we have one. We don't use open_and_lock_tables()
@ -266,6 +267,7 @@ static bool open_and_lock_table_for_truncate(THD *thd, TABLE_LIST *table_ref,
*hton_can_recreate= ha_check_storage_engine_flag(table->s->db_type(),
HTON_CAN_RECREATE);
table_ref->mdl_request.ticket= table->mdl_ticket;
}
else
{
@ -273,21 +275,12 @@ static bool open_and_lock_table_for_truncate(THD *thd, TABLE_LIST *table_ref,
Even though we could use the previous execution branch here just as
well, we must not try to open the table:
*/
MDL_request mdl_global_request, mdl_request;
MDL_request_list mdl_requests;
mdl_global_request.init(MDL_key::GLOBAL, "", "", MDL_INTENTION_EXCLUSIVE);
mdl_request.init(MDL_key::TABLE, table_ref->db, table_ref->table_name,
MDL_SHARED_NO_READ_WRITE);
mdl_requests.push_front(&mdl_request);
mdl_requests.push_front(&mdl_global_request);
if (thd->mdl_context.acquire_locks(&mdl_requests,
thd->variables.lock_wait_timeout))
DBUG_ASSERT(table_ref->next_global == NULL);
if (lock_table_names(thd, table_ref, NULL,
thd->variables.lock_wait_timeout,
MYSQL_OPEN_SKIP_TEMPORARY))
DBUG_RETURN(TRUE);
mdl_ticket= mdl_request.ticket;
if (dd_check_storage_engine_flag(thd, table_ref->db, table_ref->table_name,
HTON_CAN_RECREATE, hton_can_recreate))
DBUG_RETURN(TRUE);
@ -313,7 +306,9 @@ static bool open_and_lock_table_for_truncate(THD *thd, TABLE_LIST *table_ref,
else
{
ulong timeout= thd->variables.lock_wait_timeout;
if (thd->mdl_context.upgrade_shared_lock_to_exclusive(mdl_ticket, timeout))
if (thd->mdl_context.
upgrade_shared_lock_to_exclusive(table_ref->mdl_request.ticket,
timeout))
DBUG_RETURN(TRUE);
mysql_mutex_lock(&LOCK_open);
tdc_remove_table(thd, TDC_RT_REMOVE_ALL, table_ref->db,
@ -335,15 +330,14 @@ static bool open_and_lock_table_for_truncate(THD *thd, TABLE_LIST *table_ref,
table_ref->required_type= FRMTYPE_TABLE;
/* We don't need to load triggers. */
DBUG_ASSERT(table_ref->trg_event_map == 0);
/* Work around partition parser rules using alter table's. */
if (thd->lex->alter_info.flags & ALTER_ADMIN_PARTITION)
{
table_ref->lock_type= TL_WRITE;
table_ref->mdl_request.set_type(MDL_SHARED_WRITE);
}
/* Ensure proper lock types (e.g. from the parser). */
DBUG_ASSERT(table_ref->lock_type == TL_WRITE);
DBUG_ASSERT(table_ref->mdl_request.type == MDL_SHARED_WRITE);
/*
Even though we have an MDL lock on the table here, we don't
pass MYSQL_OPEN_HAS_MDL_LOCK to open_and_lock_tables
since to truncate a MERGE table, we must open and lock
merge children, and on those we don't have an MDL lock.
Thus clear the ticket to satisfy MDL asserts.
*/
table_ref->mdl_request.ticket= NULL;
/*
Open the table as it will handle some required preparations.