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MDEV-10356: rpl.rpl_parallel_temptable failure due to incorrect commit optimization of temptables

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The problem was that parallel replication of temporary tables using
statement-based binlogging could overlap the COMMIT in one thread with a DML
or DROP TEMPORARY TABLE in another thread using the same temporary table.
Temporary tables are not safe for concurrent access, so this caused
reference to freed memory and possibly other nastiness.

The fix is to disable the optimisation with overlapping commits of one
transaction with the start of a later transaction, when temporary tables are
in use. Then the following event groups will be blocked from starting until
the one using temporary tables is completed.

This also fixes occasional test failures of rpl.rpl_parallel_temptable seen
in Buildbot.

Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>
This commit is contained in:
Kristian Nielsen
2023-09-07 13:39:28 +02:00
parent d762e9d943
commit e937a64d46
3 changed files with 34 additions and 1 deletions
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18
sql/rpl_parallel.cc
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@ -218,6 +218,7 @@ finish_event_group(rpl_parallel_thread *rpt, uint64 sub_id,
waiting for this). In most cases (normal DML), it will be a no-op.
*/
rgi->mark_start_commit_no_lock();
rgi->commit_orderer.wakeup_blocked= false;
if (entry->last_committed_sub_id < sub_id)
{
@ -1425,7 +1426,22 @@ handle_rpl_parallel_thread(void *arg)
if (!thd->killed)
{
DEBUG_SYNC(thd, "rpl_parallel_before_mark_start_commit");
rgi->mark_start_commit();
if (thd->lex->stmt_accessed_temp_table())
{
/*
Temporary tables are special, they require strict
single-threaded use as they have no locks protecting concurrent
access. Therefore, we cannot safely use the optimization of
overlapping the commit of this transaction with the start of the
following.
So we skip the early mark_start_commit() and also block any
wakeup_subsequent_commits() until this event group is fully
done, inside finish_event_group().
*/
rgi->commit_orderer.wakeup_blocked= true;
}
else
rgi->mark_start_commit();
DEBUG_SYNC(thd, "rpl_parallel_after_mark_start_commit");
}
}