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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
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7
sql/table_cache.h
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@ -47,13 +47,14 @@ extern bool tdc_remove_table(THD *thd, enum_tdc_remove_table_type remove_type,
bool kill_delayed_threads);
extern int tdc_wait_for_old_version(THD *thd, const char *db,
const char *table_name,
ulong wait_timeout, uint deadlock_weight);
ulong wait_timeout, uint deadlock_weight,
ulong refresh_version= ULONG_MAX);
extern ulong tdc_refresh_version(void);
extern void tdc_increment_refresh_version(void);
extern ulong tdc_increment_refresh_version(void);
extern void tdc_assign_new_table_id(TABLE_SHARE *share);
extern uint tc_records(void);
extern void tc_purge(void);
extern void tc_purge(bool mark_flushed= false);
extern void tc_add_table(THD *thd, TABLE *table);
extern bool tc_release_table(TABLE *table);