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MDEV-14941 Timeouts on persistent statistics tables caused by MDEV-14511

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MDEV-14511 tried to avoid some consistency problems related to InnoDB
persistent statistics. The persistent statistics are being written by
an InnoDB internal SQL interpreter that requires the InnoDB data dictionary
cache to be locked.

Before MDEV-14511, the statistics were written during DDL in separate
transactions, which could unnecessarily reduce performance (each commit
would require a redo log flush) and break atomicity, because the statistics
would be updated separately from the dictionary transaction.

However, because it is unacceptable to hold the InnoDB data dictionary
cache locked while suspending the execution for waiting for a
transactional lock (in the mysql.innodb_index_stats or
mysql.innodb_table_stats tables) to be released, any lock conflict
was immediately be reported as "lock wait timeout".

To fix MDEV-14941, an attempt to reduce these lock conflicts by acquiring
transactional locks on the user tables in both the statistics and DDL
operations was made, but it would still not entirely prevent lock conflicts
on the mysql.innodb_index_stats and mysql.innodb_table_stats tables.

Fixing the remaining problems would require a change that is too intrusive
for a GA release series, such as MariaDB 10.2.

Thefefore, we revert the change MDEV-14511. To silence the
MDEV-13201 assertion, we use the pre-existing flag trx_t::internal.
This commit is contained in:
Marko Mäkelä
2018-01-21 18:23:28 +02:00
parent 6b7dcefdc8
commit 4f8555f1f6
18 changed files with 681 additions and 672 deletions
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2
mysql-test/suite/innodb/t/innodb_stats_drop_locked.test
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@ -57,5 +57,5 @@ SELECT table_name FROM mysql.innodb_index_stats
WHERE table_name='innodb_stats_drop_locked';
--disable_query_log
call mtr.add_suppression("Unable to delete statistics for table test\\.innodb_stats_drop_locked: Lock wait");
call mtr.add_suppression("Unable to delete statistics for table test.innodb_stats_drop_locked: Lock wait timeout. They can be deleted later using DELETE FROM mysql.innodb_index_stats WHERE database_name");
--enable_query_log