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This deadlock would occur between two connections A and B if statements where executed in the following way: 1) Connection A executes a DML statement against table s1.t1 with autocommit off. This causes a shared metadata lock on s1.t1 to be acquired. (With autocommit on, the metadata lock will be dropped once the statment completes and the deadlock will not occour.) 2) Connection B tries to DROP DATABASE s1. This will block against the metadata lock connection A holds on s1.t1. While blocking, connection B will hold the LOCK_mysql_create_db mutex. 3) Connection A tries to ALTER DATABASE s1. This will block when trying to get LOCK_mysql_create_db mutex held by connection B. 4) Deadlock between DROP DATABASE and ALTER DATABASE (which has autocommit off). If Connection A used an explicitly started transaction rather than having autocommit off, this deadlock did not happen as ALTER DATABASE is disallowed inside transactions. This patch fixes the problem by changing ALTER DATABASE to cause an implicit commit before executing. This will cause the metadata lock on s1.t1 to be dropped, allowing DROP DATABASE to proceed. This will in turn cause the LOCK_mysql_create_db mutex to be unlocked, allowing ALTER DATABASE to proceed. Note that SQL commands other than ALTER DATABASE that also use LOCK_mysql_create_db, already cause an implicit commit. Incompatible change: ALTER DATABASE (and its synonym ALTER SCHEMA) now cause an implicit commit. This must be reflected in the documentation. Test case added to schema.test. sql/sql_parse.cc: Added CF_AUTO_COMMIT_TRANS to SQLCOM_ALTER_DB. Removed thd->active_transaction() checks from SQLCOM_DROP_DB, SQLCOM_ALTER_DB_UPGRADE and SQLCOM_ALTER_DB as these statements cause an implicit commit.
This directory contains a test suite for the MySQL daemon. To run the currently existing test cases, simply execute ./mysql-test-run in this directory. It will fire up the newly built mysqld and test it. Note that you do not have to have to do "make install", and you could actually have a co-existing MySQL installation. The tests will not conflict with it. All tests must pass. If one or more of them fail on your system, please read the following manual section for instructions on how to report the problem: http://dev.mysql.com/doc/mysql/en/mysql-test-suite.html If you want to use an already running MySQL server for specific tests, use the --extern option to mysql-test-run. Please note that in this mode, the test suite expects you to provide the names of the tests to run. For example, here is the command to run the "alias" and "analyze" tests with an external server: mysql-test-run --extern alias analyze To match your setup, you might also need to provide --socket, --user, and other relevant options. With no test cases named on the command line, mysql-test-run falls back to the normal "non-extern" behavior. The reason for this is that some tests cannot run with an external server. You can create your own test cases. To create a test case, create a new file in the t subdirectory using a text editor. The file should have a .test extension. For example: xemacs t/test_case_name.test In the file, put a set of SQL statements that create some tables, load test data, and run some queries to manipulate it. We would appreciate it if you name your test tables t1, t2, t3 ... (to not conflict too much with existing tables). Your test should begin by dropping the tables you are going to create and end by dropping them again. This ensures that you can run the test over and over again. If you are using mysqltest commands (like result file names) in your test case, you should create the result file as follows: mysql-test-run --record test_case_name or mysqltest --record < t/test_case_name.test If you only have a simple test cases consisting of SQL statements and comments, you can create the test case in one of the following ways: mysql-test-run --record test_case_name mysql test < t/test_case_name.test > r/test_case_name.result mysqltest --record --record-file=r/test_case_name.result < t/test_case_name.test When this is done, take a look at r/test_case_name.result - If the result is incorrect, you have found a bug. In this case, you should edit the test result to the correct results so that we can verify that the bug is corrected in future releases. To submit your test case, put your .test file and .result file(s) into a tar.gz archive, add a README that explains the problem, ftp the archive to ftp://support.mysql.com/pub/mysql/secret/ and send a mail to bugs@lists.mysql.com