maria-developers team mailing list archive

[Sergei Golubchik <serg@xxxxxxxxxxx>]

Hi, Sergey,

I think it's fine. I had a few questions though, see below:

> commit 47aa5f9
> Author: Sergey Vojtovich <svoj@xxxxxxxxxxx>
> Date:   Fri May 6 13:44:07 2016 +0400
> 
>     MDEV-7660 - MySQL WL#6671 "Improve scalability by not using thr_lock.c locks
>                 for InnoDB tables"
>     
>     Don't use thr_lock.c locks for InnoDB tables.
>     
>     Let HANDLER READ call external_lock() even if SE is not going to be locked by
>     THR_LOCK. This fixes at least main.implicit_commit failure.
>     
>     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.
>     
>     For the very same reason partition_debug_sync test was adjusted to use MyISAM.
> 
> diff --git a/sql/sql_handler.cc b/sql/sql_handler.cc
> index e8ade81..76107ae 100644
> --- a/sql/sql_handler.cc
> +++ b/sql/sql_handler.cc
> @@ -752,11 +752,12 @@ bool mysql_ha_read(THD *thd, TABLE_LIST *tables,
>    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;

I don't understand this code in mysql_ha_read() at all :(
even before your changes

>      /* save open_tables state */
>      TABLE* backup_open_tables= thd->open_tables;
> diff --git a/storage/xtradb/handler/ha_innodb.h b/storage/xtradb/handler/ha_innodb.h
> index 2027a59..efb8120 100644
> --- a/storage/xtradb/handler/ha_innodb.h
> +++ b/storage/xtradb/handler/ha_innodb.h
> @@ -218,6 +218,7 @@ class ha_innobase: public handler
>  	bool can_switch_engines();
>  	uint referenced_by_foreign_key();
>  	void free_foreign_key_create_info(char* str);
> +	uint lock_count(void) const;
>  	THR_LOCK_DATA **store_lock(THD *thd, THR_LOCK_DATA **to,
>  					enum thr_lock_type lock_type);
>  	void init_table_handle_for_HANDLER();
> 
> commit 5645626
> Author: Sergey Vojtovich <svoj@xxxxxxxxxxx>
> Date:   Tue May 24 12:25:56 2016 +0400
> 
>     MDEV-7660 - MySQL WL#6671 "Improve scalability by not using thr_lock.c locks
>                 for InnoDB tables"
>     
>     - InnoDB now acquires shared lock for HANDLER ... READ

Why?

>     - LOCK TABLES now disables autocommit implicitely
>     - UNLOCK TABLES now re-enables autocommit implicitely if it was disabled by
>       LOCK TABLES
>     - adjusted test cases to this new behavior
> 
> diff --git a/sql/sql_base.cc b/sql/sql_base.cc
> index 3091bd6..7d39484 100644
> --- a/sql/sql_base.cc
> +++ b/sql/sql_base.cc
> @@ -2824,6 +2824,8 @@ Locked_tables_list::unlock_locked_tables(THD *thd)
>      request for metadata locks and TABLE_LIST elements.
>    */
>    reset();
> +  if (thd->variables.option_bits & OPTION_AUTOCOMMIT)
> +    thd->variables.option_bits&= ~(OPTION_NOT_AUTOCOMMIT);

1. Was it possible - before your change - for OPTION_AUTOCOMMIT and
OPTION_NOT_AUTOCOMMIT to be out of sync?

2. What if someone changes @@autocommit under LOCK TABLES?
Do you have a test for that?

3. Do you need to set SERVER_STATUS_AUTOCOMMIT here?

>  }
>  
>  
> diff --git a/mysql-test/t/innodb_mysql_lock.test b/mysql-test/t/innodb_mysql_lock.test
> index cb57c09..85ba418 100644
> --- a/mysql-test/t/innodb_mysql_lock.test
> +++ b/mysql-test/t/innodb_mysql_lock.test
> @@ -150,14 +150,16 @@ let $wait_condition=
>  --source include/wait_condition.inc
>  LOCK TABLES t1 READ;
>  SELECT release_lock('bug42147_lock');
> +let $wait_condition=
> +  SELECT COUNT(*) > 0 FROM information_schema.processlist
> +  WHERE state = 'executing'
> +  AND info = 'INSERT INTO t1 SELECT get_lock(\'bug42147_lock\', 60)';
> +--source include/wait_condition.inc
> +UNLOCK TABLES;

I don't understand the original test case. But after your changes it
actually makes sense :)

>  
>  connection default;
>  --reap
>  
> -connection con2;
> -UNLOCK TABLES;
> -
> -connection default;
>  disconnect con2;
>  DROP TABLE t1;
>  
> diff --git a/mysql-test/r/partition_explicit_prune.result b/mysql-test/r/partition_explicit_prune.result
> index 765803d..7b9c53d 100644
> --- a/mysql-test/r/partition_explicit_prune.result
> +++ b/mysql-test/r/partition_explicit_prune.result
> @@ -281,7 +281,7 @@ UNLOCK TABLES;
>  SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS
>  WHERE VARIABLE_NAME LIKE 'HANDLER_%' AND VARIABLE_VALUE > 0;
>  VARIABLE_NAME	VARIABLE_VALUE
> -HANDLER_COMMIT	2
> +HANDLER_COMMIT	3

why is that?

>  HANDLER_READ_RND_NEXT	52
>  HANDLER_TMP_WRITE	72
>  HANDLER_WRITE	2
> diff --git a/mysql-test/suite/handler/handler.inc b/mysql-test/suite/handler/handler.inc
> index b1e881f..8cad6a5 100644
> --- a/mysql-test/suite/handler/handler.inc
> +++ b/mysql-test/suite/handler/handler.inc
> @@ -1091,6 +1091,12 @@ connection default;
>  --reap
>  drop table t2;
>  
> +# This test expects "handler t1 read a next" to get blocked on table level
> +# lock so that further "drop table t1" can break the lock and close handler.
> +# This notification mechanism doesn't work with InnoDB since it bypasses
> +# table level locks.

what happens for InnoDB then?
I'd expect "handler t1 read a next" to get blocked inside the InnoDB.
what does then "drop table t1" do?

> +if ($engine_type != 'InnoDB')
> +{
>  --echo # 
>  --echo # Bug #46224 HANDLER statements within a transaction might 
>  --echo #            lead to deadlocks

Regards,
Sergei
Chief Architect MariaDB
and security@xxxxxxxxxxx