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2617.31.12, 2617.31.15, 2617.31.15, 2617.31.16, 2617.43.1 - initial changeset that introduced the fix for Bug#989 and follow up fixes for all test suite failures introduced in the initial changeset. ------------------------------------------------------------ revno: 2617.31.1 committer: Davi Arnaut <Davi.Arnaut@Sun.COM> branch nick: 4284-6.0 timestamp: Fri 2009-03-06 19:17:00 -0300 message: Bug#989: If DROP TABLE while there's an active transaction, wrong binlog order WL#4284: Transactional DDL locking Currently the MySQL server does not keep metadata locks on schema objects for the duration of a transaction, thus failing to guarantee the integrity of the schema objects being used during the transaction and to protect then from concurrent DDL operations. This also poses a problem for replication as a DDL operation might be replicated even thought there are active transactions using the object being modified. The solution is to defer the release of metadata locks until a active transaction is either committed or rolled back. This prevents other statements from modifying the table for the entire duration of the transaction. This provides commitment ordering for guaranteeing serializability across multiple transactions. - Incompatible change: If MySQL's metadata locking system encounters a lock conflict, the usual schema is to use the try and back-off technique to avoid deadlocks -- this schema consists in releasing all locks and trying to acquire them all in one go. But in a transactional context this algorithm can't be utilized as its not possible to release locks acquired during the course of the transaction without breaking the transaction commitments. To avoid deadlocks in this case, the ER_LOCK_DEADLOCK will be returned if a lock conflict is encountered during a transaction. Let's consider an example: A transaction has two statements that modify table t1, then table t2, and then commits. The first statement of the transaction will acquire a shared metadata lock on table t1, and it will be kept utill COMMIT to ensure serializability. At the moment when the second statement attempts to acquire a shared metadata lock on t2, a concurrent ALTER or DROP statement might have locked t2 exclusively. The prescription of the current locking protocol is that the acquirer of the shared lock backs off -- gives up all his current locks and retries. This implies that the entire multi-statement transaction has to be rolled back. - Incompatible change: FLUSH commands such as FLUSH PRIVILEGES and FLUSH TABLES WITH READ LOCK won't cause locked tables to be implicitly unlocked anymore.
72 lines
1.8 KiB
Text
72 lines
1.8 KiB
Text
# Let's see if FLUSH TABLES WITH READ LOCK blocks COMMIT of existing
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# transactions.
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# We verify that we did not introduce a deadlock.
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# This is intended to mimick how mysqldump and innobackup work.
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--source include/have_log_bin.inc
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# And it requires InnoDB
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--source include/have_log_bin.inc
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--source include/have_innodb.inc
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--echo # Save the initial number of concurrent sessions
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--source include/count_sessions.inc
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--echo # Establish connection con1 (user=root)
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connect (con1,localhost,root,,);
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--echo # Establish connection con2 (user=root)
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connect (con2,localhost,root,,);
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# FLUSH TABLES WITH READ LOCK should block writes to binlog too
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--echo # Switch to connection con1
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connection con1;
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CREATE TABLE t1 (a INT) ENGINE=innodb;
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RESET MASTER;
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SET AUTOCOMMIT=0;
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SELECT 1;
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--echo # Switch to connection con2
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connection con2;
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FLUSH TABLES WITH READ LOCK;
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SHOW MASTER STATUS;
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--echo # Switch to connection con1
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connection con1;
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send INSERT INTO t1 VALUES (1);
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--echo # Switch to connection con2
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connection con2;
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sleep 1;
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SHOW MASTER STATUS;
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UNLOCK TABLES;
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--echo # Switch to connection con1
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connection con1;
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reap;
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DROP TABLE t1;
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SET AUTOCOMMIT=1;
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# GLR blocks new transactions
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create table t1 (a int) engine=innodb;
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connection con1;
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flush tables with read lock;
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connection con2;
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begin;
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--send insert into t1 values (1);
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connection con1;
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let $wait_condition=
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select count(*) = 1 from information_schema.processlist
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where state = "Waiting for release of readlock" and
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info = "insert into t1 values (1)";
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--source include/wait_condition.inc
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unlock tables;
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connection con2;
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--reap
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commit;
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drop table t1;
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--echo # Switch to connection default and close connections con1 and con2
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connection default;
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disconnect con1;
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disconnect con2;
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--echo # Wait till all disconnects are completed
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--source include/wait_until_count_sessions.inc
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