In commit 1bd681c8b3 (MDEV-25506 part 3)
we introduced a "fake instant timeout" when a transaction would wait
for a table or record lock while holding dict_sys.latch. This prevented
a deadlock of the server but could cause bogus errors for operations
on the InnoDB persistent statistics tables.
A better fix is to ensure that whenever a transaction is being
executed in the InnoDB internal SQL parser (which will for now
require dict_sys.latch to be held), it will already have acquired
all locks that could be required for the execution. So, we will
acquire the following locks upfront, before acquiring dict_sys.latch:
(1) MDL on the affected user table (acquired by the SQL layer)
(2) If applicable (not for RENAME TABLE): InnoDB table lock
(3) If persistent statistics are going to be modified:
(3.a) MDL_SHARED on mysql.innodb_table_stats, mysql.innodb_index_stats
(3.b) exclusive table locks on the statistics tables
(4) Exclusive table locks on the InnoDB data dictionary tables
(not needed in ANALYZE TABLE and the like)
Note: Acquiring exclusive locks on the statistics tables may cause
more locking conflicts between concurrent DDL operations.
Notably, RENAME TABLE will lock the statistics tables
even if no persistent statistics are enabled for the table.
DROP DATABASE will only acquire locks on statistics tables if
persistent statistics are enabled for the tables on which the
SQL layer is invoking ha_innobase::delete_table().
For any "garbage collection" in innodb_drop_database(), a timeout
while acquiring locks on the statistics tables will result in any
statistics not being deleted for any tables that the SQL layer
did not know about.
If innodb_defragment=ON, information may be written to the statistics
tables even for tables for which InnoDB persistent statistics are
disabled. But, DROP TABLE will no longer attempt to delete that
information if persistent statistics are not enabled for the table.
This change should also fix the hangs related to InnoDB persistent
statistics and STATS_AUTO_RECALC (MDEV-15020) as well as
a bug that running ALTER TABLE on the statistics tables
concurrently with running ALTER TABLE on InnoDB tables could
cause trouble.
lock_rec_enqueue_waiting(), lock_table_enqueue_waiting():
Do not issue a fake instant timeout error when the transaction
is holding dict_sys.latch. Instead, assert that the dict_sys.latch
is never being held here.
lock_sys_tables(): A new function to acquire exclusive locks on all
dictionary tables, in case DROP TABLE or similar operation is
being executed. Locking non-hard-coded tables is optional to avoid
a crash in row_merge_drop_temp_indexes(). The SYS_VIRTUAL table was
introduced in MySQL 5.7 and MariaDB Server 10.2. Normally, we require
all these dictionary tables to exist before executing any DDL, but
the function row_merge_drop_temp_indexes() is an exception.
When upgrading from MariaDB Server 10.1 or MySQL 5.6 or earlier,
the table SYS_VIRTUAL would not exist at this point.
ha_innobase::commit_inplace_alter_table(): Invoke
log_write_up_to() while not holding dict_sys.latch.
dict_sys_t::remove(), dict_table_close(): No longer try to
drop index stubs that were left behind by aborted online ADD INDEX.
Such indexes should be dropped from the InnoDB data dictionary by
row_merge_drop_indexes() as part of the failed DDL operation.
Stubs for aborted indexes may only be left behind in the
data dictionary cache.
dict_stats_fetch_from_ps(): Use a normal read-only transaction.
ha_innobase::delete_table(), ha_innobase::truncate(), fts_lock_table():
While waiting for purge to stop using the table,
do not hold dict_sys.latch.
ha_innobase::delete_table(): Implement a work-around for the rollback
of ALTER TABLE...ADD PARTITION. MDL_EXCLUSIVE would not be held if
ALTER TABLE hits lock_wait_timeout while trying to upgrade the MDL
due to a conflicting LOCK TABLES, such as in the first ALTER TABLE
in the test case of Bug#53676 in parts.partition_special_innodb.
Therefore, we must explicitly stop purge, because it would not be
stopped by MDL.
dict_stats_func(), btr_defragment_chunk(): Allocate a THD so that
we can acquire MDL on the InnoDB persistent statistics tables.
mysqltest_embedded: Invoke ha_pre_shutdown() before free_used_memory()
in order to avoid ASAN heap-use-after-free related to acquire_thd().
trx_t::dict_operation_lock_mode: Changed the type to bool.
row_mysql_lock_data_dictionary(), row_mysql_unlock_data_dictionary():
Implemented as macros.
rollback_inplace_alter_table(): Apply an infinite timeout to lock waits.
innodb_thd_increment_pending_ops(): Wrapper for
thd_increment_pending_ops(). Never attempt async operation for
InnoDB background threads, such as the trx_t::commit() in
dict_stats_process_entry_from_recalc_pool().
lock_sys_t::cancel(trx_t*): Make dictionary transactions immune to KILL.
lock_wait(): Make dictionary transactions immune to KILL, and to
lock wait timeout when waiting for locks on dictionary tables.
parts.partition_special_innodb: Use lock_wait_timeout=0 to instantly
get ER_LOCK_WAIT_TIMEOUT.
main.mdl: Filter out MDL on InnoDB persistent statistics tables
Reviewed by: Thirunarayanan Balathandayuthapani
This is a backport of 161e4bfafd.
trans_rollback_to_savepoint(): Only release metadata locks (MDL)
if the storage engines agree, after the changes were already rolled back.
Ever since commit 3792693f31
and mysql/mysql-server@55ceedbc3f
we used to cheat here and always release MDL if the binlog is disabled.
MDL are supposed to prevent race conditions between DML and DDL also
when no replication is in use. MDL are supposed to be a superset of
InnoDB table locks: InnoDB table lock may only exist if the thread
also holds MDL on the table name.
In the included test case, ROLLBACK TO SAVEPOINT would wrongly release
the MDL on both tables and let ALTER TABLE proceed, even though the DML
transaction is actually holding locks on the table.
Until commit 1bd681c8b3 (MDEV-25506)
in MariaDB 10.6, InnoDB would often work around the locking violation
in a blatantly non-ACID way: If locks exist on a table that is being
dropped (in this case, actually a partition of a table that is being
rebuilt by ALTER TABLE), InnoDB could move the table (or partition)
into a queue, to be dropped after the locks and references had been
released. If the lock is not released and the original copy of the
table not dropped quickly enough, a name conflict could occur on
a subsequent ALTER TABLE.
The scenario of commit 3792693f31
is unaffected by this fix, because mysqldump
would use non-locking reads, and the transaction would not be holding
any InnoDB locks during the execution of ROLLBACK TO SAVEPOINT.
MVCC reads inside InnoDB are only covered by MDL and page latches,
not by any table or record locks.
FIXME: It would be nice if storage engines were specifically asked
which MDL can be released, instead of only offering a choice
between all or nothing. InnoDB should be able to release any
locks for tables that are no longer in trx_t::mod_tables, except
if another transaction had converted some implicit record locks
to explicit ones, before the ROLLBACK TO SAVEPOINT had been completed.
Reviewed by: Sergei Golubchik
InnoDB does not allow FOREIGN KEY constraints to exist for TEMPORARY TABLE.
InnoDB introduced a dedicated tablespace for temporary tables, and actually
stopped creating persistent metadata and data for temporary tables.
row_table_add_foreign_constraints(): Do not create a persistent
transaction.
dict_create_foreign_constraints_low(): Add the persistent transaction to
the update the foreign key relation in dictionary.
dict_create_foreign_constraints_low(): Remove a duplicated check for
partitioned tables.
