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MDEV-28930 ALTER TABLE Deadlocks with parallel TL_WRITE

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ALTER ONLINE TABLE acquires table with TL_READ. Myisam normally acquires
TL_WRITE for DML, which makes it hang until table is freed.

We deadlock once ALTER upgrades its MDL lock.

Solution:
Unlock table earlier. We don't need to hold TL_READ once we finished
copying. Relay log replication requires no data locks on `from` table.
This commit is contained in:
Nikita Malyavin
2022-06-29 20:16:19 +03:00
committed by Sergei Golubchik
parent 8fbdc76038
commit 2ed03a41e6
5 changed files with 65 additions and 9 deletions
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21
mysql-test/main/alter_table_online_debug.result
View File

@ -579,6 +579,27 @@ drop table t1;
drop table t2;
drop table t3;
#
# MDEV-28930 ALTER TABLE Deadlocks with parallel TL_WRITE
#
create table t1(a int) engine=myisam select 1;
set debug_sync='alter_table_online_before_lock SIGNAL ready WAIT_FOR go_for_locking';
alter table t1 force;
connection con2;
set debug_sync='now WAIT_FOR ready';
set debug_sync='thr_multi_lock_before_thr_lock SIGNAL go_for_locking';
update t1 set a=2;
connection default;
set debug_sync='alter_table_online_before_lock SIGNAL ready WAIT_FOR go_for_locking';
alter table mysql.global_priv force;
connection con2;
set debug_sync='now WAIT_FOR ready';
set debug_sync='thr_multi_lock_before_thr_lock SIGNAL go_for_locking';
create user user1@localhost;
connection default;
set debug_sync=reset;
drop user user1@localhost;
drop table t1;
#
# MDEV-28959 Online alter ignores strict table mode
#
create table t1 (a int);

33
mysql-test/main/alter_table_online_debug.test
View File

@ -717,6 +717,39 @@ drop table t1;
drop table t2;
drop table t3;
--echo #
--echo # MDEV-28930 ALTER TABLE Deadlocks with parallel TL_WRITE
--echo #
create table t1(a int) engine=myisam select 1;
set debug_sync='alter_table_online_before_lock SIGNAL ready WAIT_FOR go_for_locking';
--send
alter table t1 force;
--connection con2
set debug_sync='now WAIT_FOR ready';
set debug_sync='thr_multi_lock_before_thr_lock SIGNAL go_for_locking';
update t1 set a=2;
--connection default
--reap
set debug_sync='alter_table_online_before_lock SIGNAL ready WAIT_FOR go_for_locking';
--send
alter table mysql.global_priv force;
--connection con2
set debug_sync='now WAIT_FOR ready';
set debug_sync='thr_multi_lock_before_thr_lock SIGNAL go_for_locking';
create user user1@localhost;
--connection default
--reap
set debug_sync=reset;
drop user user1@localhost;
drop table t1;
--echo #
--echo # MDEV-28959 Online alter ignores strict table mode
--echo #

6
mysql-test/suite/perfschema/r/alter_table_progress.result
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@ -75,17 +75,15 @@ stage/sql/table lock NULL NULL
stage/sql/After create NULL NULL
stage/sql/copy to tmp table 5 5
stage/sql/Enabling keys NULL NULL
stage/sql/Unlocking tables NULL NULL
stage/sql/Enabling keys NULL NULL
stage/sql/Apply log event NULL NULL
stage/sql/After apply log event NULL NULL
stage/sql/Rename result table NULL NULL
stage/sql/Unlocking tables NULL NULL
stage/sql/Rename result table NULL NULL
stage/sql/End of update loop NULL NULL
stage/sql/Query end NULL NULL
stage/sql/Commit NULL NULL
stage/sql/closing tables NULL NULL
stage/sql/Unlocking tables NULL NULL
stage/sql/closing tables NULL NULL
stage/sql/Commit implicit NULL NULL
stage/sql/Starting cleanup NULL NULL
stage/sql/Freeing items NULL NULL

9
sql/log_event_server.cc
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@ -4781,12 +4781,11 @@ int Rows_log_event::do_apply_event(rpl_group_info *rgi)
thd->set_query_timer();
/*
If there is no locks taken, this is the first binrow event seen
after the table map events. We should then lock all the tables
used in the transaction and proceed with execution of the actual
event.
If there are no tables open, this must be the first row event seen
after the table map events. We should then open and lock all tables
used in the transaction and proceed with execution of the actual event.
*/
if (!thd->lock)
if (!thd->open_tables)
{
/*
Lock_tables() reads the contents of thd->lex, so they must be

5
sql/sql_table.cc
View File

@ -11998,6 +11998,11 @@ copy_data_between_tables(THD *thd, TABLE *from, TABLE *to,
// We restore bitmaps, because update event is going to mess up with them.
to->default_column_bitmaps();
end_read_record(&info);
init_read_record_done= false;
mysql_unlock_tables(thd, thd->lock);
thd->lock= NULL;
error= online_alter_read_from_binlog(thd, &rgi, binlog);
DEBUG_SYNC(thd, "alter_table_online_before_lock");