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MDEV-5492 - Reduce usage of LOCK_open: TABLE::in_use

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Move TABLE::in_use out of LOCK_open.

This is done with assumtion that foreign threads accessing TABLE::in_use
will only need consistent value _after_ marking table for flush and purging
unused table instances. In this case TABLE::in_use will always point to a
valid thread object.

Previously FLUSH TABLES thread may wait for tables flushed subsequently by
concurrent threads which breaks the above assumption, e.g.:
open tables: t1 (version= 1)
thr1 (FLUSH TABLES): refresh_version++
thr1 (FLUSH TABLES): purge table cache
open tables: none
thr2 (SELECT * FROM t1): open tables: t1
open tables: t1 (version= 2)
thr2 (FLUSH TABLES): refresh_version++
thr2 (FLUSH TABLES): purge table cache
thr1 (FLUSH TABLES): wait for old tables (including t1 with version 2)

It is fixed so that FLUSH TABLES waits only for tables that were open
heretofore.
This commit is contained in:
Sergey Vojtovich
2014-02-13 10:44:10 +04:00
parent a25d87e50f
commit 048e9c40a6
8 changed files with 83 additions and 120 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
sql/sql_base.cc
View File

@ -385,7 +385,8 @@ void kill_delayed_threads_for_table(TABLE_SHARE *share)
{
THD *in_use= tab->in_use;
if (in_use && (in_use->system_thread & SYSTEM_THREAD_DELAYED_INSERT) &&
DBUG_ASSERT(in_use && tab->s->tdc.flushed);
if ((in_use->system_thread & SYSTEM_THREAD_DELAYED_INSERT) &&
! in_use->killed)
{
in_use->killed= KILL_SYSTEM_THREAD;
@ -426,9 +427,12 @@ bool close_cached_tables(THD *thd, TABLE_LIST *tables,
{
bool result= FALSE;
struct timespec abstime;
ulong refresh_version;
DBUG_ENTER("close_cached_tables");
DBUG_ASSERT(thd || (!wait_for_refresh && !tables));
refresh_version= tdc_increment_refresh_version();
if (!tables)
{
/*
@ -438,13 +442,12 @@ bool close_cached_tables(THD *thd, TABLE_LIST *tables,
incrementing of refresh_version is followed by purge of unused table
shares.
*/
tdc_increment_refresh_version();
kill_delayed_threads();
/*
Get rid of all unused TABLE and TABLE_SHARE instances. By doing
this we automatically close all tables which were marked as "old".
*/
tc_purge();
tc_purge(true);
/* Free table shares which were not freed implicitly by loop above. */
tdc_purge(true);
}
@ -526,7 +529,7 @@ bool close_cached_tables(THD *thd, TABLE_LIST *tables,
while ((share= tdc_it.next()))
{
mysql_mutex_lock(&share->tdc.LOCK_table_share);
if (share->has_old_version())
if (share->tdc.flushed && share->tdc.version < refresh_version)
{
/* wait_for_old_version() will unlock mutex and free share */
found= true;
@ -554,7 +557,8 @@ bool close_cached_tables(THD *thd, TABLE_LIST *tables,
if (thd->killed)
break;
if (tdc_wait_for_old_version(thd, table->db, table->table_name, timeout,
MDL_wait_for_subgraph::DEADLOCK_WEIGHT_DDL))
MDL_wait_for_subgraph::DEADLOCK_WEIGHT_DDL,
refresh_version))
{
result= TRUE;
break;
@ -1754,7 +1758,7 @@ bool wait_while_table_is_used(THD *thd, TABLE *table,
DBUG_ENTER("wait_while_table_is_used");
DBUG_PRINT("enter", ("table: '%s' share: 0x%lx db_stat: %u version: %lu",
table->s->table_name.str, (ulong) table->s,
table->db_stat, table->s->version));
table->db_stat, table->s->tdc.version));
if (thd->mdl_context.upgrade_shared_lock(
table->mdl_ticket, MDL_EXCLUSIVE,
@ -2321,7 +2325,7 @@ retry_share:
/*
Check if this TABLE_SHARE-object corresponds to a view. Note, that there is
no need to call TABLE_SHARE::has_old_version() as we do for regular tables,
no need to check TABLE_SHARE::tdc.flushed as we do for regular tables,
because view shares are always up to date.
*/
if (share->is_view)
@ -2362,7 +2366,7 @@ retry_share:
if (!(flags & MYSQL_OPEN_IGNORE_FLUSH))
{
if (share->has_old_version())
if (share->tdc.flushed)
{
/*
We already have an MDL lock. But we have encountered an old
@ -2394,7 +2398,7 @@ retry_share:
goto retry_share;
}
if (thd->open_tables && thd->open_tables->s->version != share->version)
if (thd->open_tables && thd->open_tables->s->tdc.flushed)
{
/*
If the version changes while we're opening the tables,