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MDEV-7660 - MySQL WL#6671 "Improve scalability by not using thr_lock.c locks

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for InnoDB tables"

Don't use thr_lock.c locks for InnoDB tables. Below is list of changes that
were needed to implement this:
- HANDLER OPEN acquireis MDL_SHARED_READ instead of MDL_SHARED
- HANDLER READ calls external_lock() even if SE is not going to be locked by
  THR_LOCK
- InnoDB lock wait timeouts are now honored which are much shorter by default
  than server lock wait timeouts (1 year vs 50 seconds)
- with @@autocommit= 1 LOCK TABLES disables autocommit implicitely, though
  user still sees @@autocommt= 1
- the above starts implicit transaction
- transactions started by LOCK TABLES are now rolled back on disconnect
  (previously everything was committed due to autocommit)
- transactions started by LOCK TABLES are now rolled back by ROLLBACK
  (previously everything was committed due to autocommit)
- it is now impossible to change BINLOG_FORMAT under LOCK TABLES (at least
  to statement) due to running transaction
- LOCK TABLES WRITE is additionally handled by MDL
- ...in contrast LOCK TABLES READ protection against DML is pure InnoDB
- combining transactional and non-transactional tables under LOCK TABLES
  may cause rolled back changes in transactional table and "committed"
  changes in non-transactional table
- user may disable innodb_table_locks, which will cause LOCK TABLES to be
  noop basically

Removed tests for BUG#45143 and BUG#55930 which cover InnoDB + THR_LOCK. To
operate properly these tests require code flow to go through THR_LOCK debug
sync points, which is not the case after this patch. These tests are removed
by WL#6671 as well. An alternative is to port them to different storage engine.
This commit is contained in:
Sergey Vojtovich
2016-05-06 13:44:07 +04:00
parent e2d6912609
commit d665e79c5b
31 changed files with 151 additions and 1034 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
sql/sql_handler.cc
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@ -282,7 +282,7 @@ bool mysql_ha_open(THD *thd, TABLE_LIST *tables, SQL_HANDLER *reopen)
back-off for such locks.
*/
tables->mdl_request.init(MDL_key::TABLE, tables->db, tables->table_name,
MDL_SHARED, MDL_TRANSACTION);
MDL_SHARED_READ, MDL_TRANSACTION);
mdl_savepoint= thd->mdl_context.mdl_savepoint();
/* for now HANDLER can be used only for real TABLES */
@ -750,11 +750,12 @@ retry:
tables->table= table; // This is used by fix_fields
table->pos_in_table_list= tables;
if (handler->lock->lock_count > 0)
if (handler->lock->table_count > 0)
{
int lock_error;
handler->lock->locks[0]->type= handler->lock->locks[0]->org_type;
if (handler->lock->lock_count > 0)
handler->lock->locks[0]->type= handler->lock->locks[0]->org_type;
/* save open_tables state */
TABLE* backup_open_tables= thd->open_tables;