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MDEV-5914: Parallel replication deadlock due to InnoDB lock conflicts

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Due to how gap locks work, two transactions could group commit together on the
master, but get lock conflicts and then deadlock due to different thread
scheduling order on slave.

For now, remove these deadlocks by running the parallel slave in READ
COMMITTED mode. And let InnoDB/XtraDB allow statement-based binlogging for the
parallel slave in READ COMMITTED.

We are also investigating a different solution long-term, which is based on
relaxing the gap locks only between the transactions running in parallel for
one slave, but not against possibly external transactions.
This commit is contained in:
unknown
2014-03-21 13:30:55 +01:00
parent a5418c5540
commit b352969118
10 changed files with 174 additions and 6 deletions
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6
sql/sql_class.cc
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@@ -4234,6 +4234,12 @@ extern "C" int thd_slave_thread(const MYSQL_THD thd)
return(thd->slave_thread);
}
/* Returns true for a worker thread in parallel replication. */
extern "C" int thd_rpl_is_parallel(const MYSQL_THD thd)
{
return thd->rgi_slave && thd->rgi_slave->is_parallel_exec;
}
extern "C" int thd_non_transactional_update(const MYSQL_THD thd)
{
return(thd->transaction.all.modified_non_trans_table);