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In auto-commit mode, updating both trx and non-trx tables (i.e. issuing a mixed statement) causes the following sequence of events: 1 - "Flush trx changes" (MYSQL_BIN_LOG::write) - T1: 1.1 - mutex_lock (&LOCK_log) 1.2 - mutex_lock (&LOCK_prep_xids) 1.3 - increase prepared_xids 1.4 - mutex_unlock (&LOCK_prep_xids) 1.5 - mutex_unlock (&LOCK_log) 2 - "Flush non-trx changes" (MYSQL_BIN_LOG::write) - T1: 2.1 - mutex_lock (&LOCK_log) 2.2 - mutex_unlock (&LOCK_log) 3. "unlog" - T1 3.1 - mutex_lock (&LOCK_prep_xids) 3.2 - decrease prepared xids 3.3 - pthread_cond_signal(&COND_prep_xids); 3.4 - mutex_unlock (&LOCK_prep_xids) The "FLUSH logs" command produces the following sequence of events: 1 - "FLUSH logs" command (MYSQL_BIN_LOG::new_file_impl) - user thread: 1.1 - mutex_lock (&LOCK_log) 1.2 - mutex_lock (&LOCK_prep_xids) 1.3 - while (prepared_xids) pthread_cond_wait(..., &LOCK_prep_xids); 1.4 - mutex_unlock (&LOCK_prep_xids) 1.5 - mutex_unlock (&LOCK_log) A deadlock will arise if T1 flushes the trx changes and thus increases prepared_xids but before it is able to continue the execution and flush the non-trx changes, an user thread calls the "FLUSH logs" command and wait that the prepared_xids is decreased and gets to zero. However, T1 cannot proceed with the call to "Flush non-trx changes" because it will block in the mutex "LOCK_log" and by consequence cannot complete the execution and call the unlog to decrease the prepared_xids. To fix the problem, we ensure that the non-trx changes are always flushed before the trx changes. Note that if you call "Flush non-trx changes" and a concurrent "FLUSH logs" is issued, the "Flush non-trx changes" may block, but a deadlock will never happen because the prepared_xids will eventually get to zero. Bottom line, there will not be any transaction able to increase the prepared_xids because they will block in the mutex "LOCK_log" (MYSQL_BIN_LOG::write) and those that increased the prepared_xids will eventually commit and decrease the prepared_xids.
175 lines
6.3 KiB
Text
175 lines
6.3 KiB
Text
SET BINLOG_FORMAT=MIXED;
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RESET MASTER;
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CREATE TABLE t1 (a INT PRIMARY KEY, b INT) ENGINE=INNODB;
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INSERT INTO t1 VALUES (1,1),(2,2),(3,3),(4,4),(5,5),(6,6);
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BEGIN;
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SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;
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UPDATE t1 SET b = 2*a WHERE a > 1;
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COMMIT;
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BEGIN;
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SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED;
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UPDATE t1 SET b = a * a WHERE a > 3;
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COMMIT;
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SET BINLOG_FORMAT=STATEMENT;
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BEGIN;
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SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
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UPDATE t1 SET b = 1*a WHERE a > 1;
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ERROR HY000: Cannot execute statement: binlogging impossible since BINLOG_FORMAT = STATEMENT and at least one table uses a storage engine limited to row-logging. InnoDB is limited to row-logging when transaction isolation level is READ COMMITTED or READ UNCOMMITTED.
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COMMIT;
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BEGIN;
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SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED;
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UPDATE t1 SET b = 2*a WHERE a > 2;
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ERROR HY000: Cannot execute statement: binlogging impossible since BINLOG_FORMAT = STATEMENT and at least one table uses a storage engine limited to row-logging. InnoDB is limited to row-logging when transaction isolation level is READ COMMITTED or READ UNCOMMITTED.
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COMMIT;
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BEGIN;
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SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;
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UPDATE t1 SET b = 3*a WHERE a > 3;
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COMMIT;
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BEGIN;
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SET SESSION TRANSACTION ISOLATION LEVEL SERIALIZABLE;
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UPDATE t1 SET b = 4*a WHERE a > 4;
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COMMIT;
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SET BINLOG_FORMAT=MIXED;
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BEGIN;
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SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
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UPDATE t1 SET b = 1*a WHERE a > 1;
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COMMIT;
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BEGIN;
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SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED;
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UPDATE t1 SET b = 2*a WHERE a > 2;
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COMMIT;
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BEGIN;
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SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;
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UPDATE t1 SET b = 3*a WHERE a > 3;
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COMMIT;
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BEGIN;
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SET SESSION TRANSACTION ISOLATION LEVEL SERIALIZABLE;
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UPDATE t1 SET b = 4*a WHERE a > 4;
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COMMIT;
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SET BINLOG_FORMAT=ROW;
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BEGIN;
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SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
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UPDATE t1 SET b = 1*a WHERE a > 1;
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COMMIT;
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BEGIN;
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SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED;
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UPDATE t1 SET b = 2*a WHERE a > 2;
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COMMIT;
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BEGIN;
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SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;
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UPDATE t1 SET b = 3*a WHERE a > 3;
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COMMIT;
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BEGIN;
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SET SESSION TRANSACTION ISOLATION LEVEL SERIALIZABLE;
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UPDATE t1 SET b = 4*a WHERE a > 4;
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COMMIT;
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show binlog events from <binlog_start>;
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Log_name Pos Event_type Server_id End_log_pos Info
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master-bin.000001 # Query # # use `test`; CREATE TABLE t1 (a INT PRIMARY KEY, b INT) ENGINE=INNODB
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master-bin.000001 # Query # # BEGIN
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master-bin.000001 # Query # # use `test`; INSERT INTO t1 VALUES (1,1),(2,2),(3,3),(4,4),(5,5),(6,6)
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master-bin.000001 # Xid # # COMMIT /* XID */
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master-bin.000001 # Query # # BEGIN
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master-bin.000001 # Query # # use `test`; UPDATE t1 SET b = 2*a WHERE a > 1
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master-bin.000001 # Xid # # COMMIT /* XID */
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master-bin.000001 # Query # # BEGIN
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master-bin.000001 # Table_map # # table_id: # (test.t1)
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master-bin.000001 # Update_rows # # table_id: # flags: STMT_END_F
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master-bin.000001 # Xid # # COMMIT /* XID */
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master-bin.000001 # Query # # BEGIN
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master-bin.000001 # Query # # use `test`; UPDATE t1 SET b = 3*a WHERE a > 3
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master-bin.000001 # Xid # # COMMIT /* XID */
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master-bin.000001 # Query # # BEGIN
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master-bin.000001 # Query # # use `test`; UPDATE t1 SET b = 4*a WHERE a > 4
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master-bin.000001 # Xid # # COMMIT /* XID */
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master-bin.000001 # Query # # BEGIN
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master-bin.000001 # Table_map # # table_id: # (test.t1)
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master-bin.000001 # Update_rows # # table_id: # flags: STMT_END_F
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master-bin.000001 # Xid # # COMMIT /* XID */
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master-bin.000001 # Query # # BEGIN
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master-bin.000001 # Table_map # # table_id: # (test.t1)
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master-bin.000001 # Update_rows # # table_id: # flags: STMT_END_F
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master-bin.000001 # Xid # # COMMIT /* XID */
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master-bin.000001 # Query # # BEGIN
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master-bin.000001 # Query # # use `test`; UPDATE t1 SET b = 3*a WHERE a > 3
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master-bin.000001 # Xid # # COMMIT /* XID */
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master-bin.000001 # Query # # BEGIN
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master-bin.000001 # Query # # use `test`; UPDATE t1 SET b = 4*a WHERE a > 4
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master-bin.000001 # Xid # # COMMIT /* XID */
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master-bin.000001 # Query # # BEGIN
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master-bin.000001 # Table_map # # table_id: # (test.t1)
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master-bin.000001 # Update_rows # # table_id: # flags: STMT_END_F
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master-bin.000001 # Xid # # COMMIT /* XID */
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master-bin.000001 # Query # # BEGIN
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master-bin.000001 # Table_map # # table_id: # (test.t1)
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master-bin.000001 # Update_rows # # table_id: # flags: STMT_END_F
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master-bin.000001 # Xid # # COMMIT /* XID */
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master-bin.000001 # Query # # BEGIN
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master-bin.000001 # Table_map # # table_id: # (test.t1)
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master-bin.000001 # Update_rows # # table_id: # flags: STMT_END_F
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master-bin.000001 # Xid # # COMMIT /* XID */
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master-bin.000001 # Query # # BEGIN
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master-bin.000001 # Table_map # # table_id: # (test.t1)
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master-bin.000001 # Update_rows # # table_id: # flags: STMT_END_F
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master-bin.000001 # Xid # # COMMIT /* XID */
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DROP TABLE t1;
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flush status;
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show status like "binlog_cache_use";
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Variable_name Value
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Binlog_cache_use 0
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show status like "binlog_cache_disk_use";
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Variable_name Value
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Binlog_cache_disk_use 0
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create table t1 (a int) engine=innodb;
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show status like "binlog_cache_use";
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Variable_name Value
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Binlog_cache_use 2
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show status like "binlog_cache_disk_use";
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Variable_name Value
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Binlog_cache_disk_use 1
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begin;
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delete from t1;
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commit;
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show status like "binlog_cache_use";
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Variable_name Value
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Binlog_cache_use 4
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show status like "binlog_cache_disk_use";
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Variable_name Value
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Binlog_cache_disk_use 1
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drop table t1;
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CREATE TABLE `t1` (
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`a` int(11) NOT NULL auto_increment,
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`b` int(11) default NULL,
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PRIMARY KEY (`a`)
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) ENGINE=MyISAM DEFAULT CHARSET=latin1 ;
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CREATE TABLE `t2` (
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`a` int(11) NOT NULL auto_increment,
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`b` int(11) default NULL,
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PRIMARY KEY (`a`)
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) ENGINE=INNODB DEFAULT CHARSET=latin1 ;
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insert into t1 values (1,1),(2,2);
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insert into t2 values (1,1),(4,4);
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reset master;
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UPDATE t2,t1 SET t2.a=t1.a+2;
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ERROR 23000: Duplicate entry '3' for key 'PRIMARY'
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select * from t2 /* must be (3,1), (4,4) */;
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a b
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1 1
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4 4
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there must no UPDATE in binlog
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show master status;
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File Position Binlog_Do_DB Binlog_Ignore_DB
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master-bin.000001 # <Binlog_Do_DB> <Binlog_Ignore_DB>
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delete from t1;
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delete from t2;
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insert into t1 values (1,2),(3,4),(4,4);
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insert into t2 values (1,2),(3,4),(4,4);
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reset master;
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UPDATE t2,t1 SET t2.a=t2.b where t2.a=t1.a;
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ERROR 23000: Duplicate entry '4' for key 'PRIMARY'
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there must no UPDATE in binlog
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show master status;
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File Position Binlog_Do_DB Binlog_Ignore_DB
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master-bin.000001 # <Binlog_Do_DB> <Binlog_Ignore_DB>
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drop table t1, t2;
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End of tests
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