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MWL#116: Efficient group commit

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Tweak the commit_ordered() semantics. Now it is only called for transactions
that go through 2-phase commit. This avoids forcing engines to make commits
visible before they are durable.

Also take LOCK_commit_ordered() around START TRANSACTION WITH CONSISTENT
SNAPSHOT, to get a truly consistent snapshot.
This commit is contained in:
unknown
2010-10-04 20:40:31 +02:00
parent 498f10a2be
commit 8bc445360e
4 changed files with 117 additions and 98 deletions
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31
sql/handler.cc
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@ -1251,32 +1251,7 @@ int ha_commit_one_phase(THD *thd, bool all)
enclosing 'all' transaction is rolled back.
*/
bool is_real_trans=all || thd->transaction.all.ha_list == 0;
Ha_trx_info *ha_info= trans->ha_list;
DBUG_ENTER("ha_commit_one_phase");
#ifdef USING_TRANSACTIONS
if (ha_info)
{
if (is_real_trans)
{
bool locked= false;
for (; ha_info; ha_info= ha_info->next())
{
handlerton *ht= ha_info->ht();
if (ht->commit_ordered)
{
if (ha_info->is_trx_read_write() && !locked)
{
pthread_mutex_lock(&LOCK_commit_ordered);
locked= 1;
}
ht->commit_ordered(ht, thd, all);
}
}
if (locked)
pthread_mutex_unlock(&LOCK_commit_ordered);
}
}
#endif /* USING_TRANSACTIONS */
DBUG_RETURN(commit_one_phase_2(thd, all, trans, is_real_trans));
}
@ -1901,7 +1876,13 @@ int ha_start_consistent_snapshot(THD *thd)
{
bool warn= true;
/*
Holding the LOCK_commit_ordered mutex ensures that for any transaction
we either see it committed in all engines, or in none.
*/
pthread_mutex_lock(&LOCK_commit_ordered);
plugin_foreach(thd, snapshot_handlerton, MYSQL_STORAGE_ENGINE_PLUGIN, &warn);
pthread_mutex_unlock(&LOCK_commit_ordered);
/*
Same idea as when one wants to CREATE TABLE in one engine which does not