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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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2
sql/sql_handler.cc
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@ -1135,7 +1135,7 @@ void mysql_ha_flush(THD *thd)
((hash_tables->table->mdl_ticket &&
hash_tables->table->mdl_ticket->has_pending_conflicting_lock()) ||
(!hash_tables->table->s->tmp_table &&
hash_tables->table->s->has_old_version())))
hash_tables->table->s->tdc.flushed)))
mysql_ha_close_table(hash_tables);
}