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26 MySQL Internals

This chapter describes a lot of things that you need to know when working on the MySQL code. If you plan to contribute to MySQL development, want to have access to the bleeding-edge in-between versions code, or just want to keep track of development, follow the instructions in See section 4.8 Installing from the Development Source Tree. If you are interested in MySQL internals, you should also subscribe to internals@lists.mysql.com. This is a relatively low traffic list, in comparison with mysql@lists.mysql.com.

26.1 MySQL Threads

The MySQL server creates the following threads:

mysqladmin processlist only shows the connection, INSERT DELAYED, and replication threads.

26.2 MySQL Test Suite

Until recently, our main full-coverage test suite was based on proprietary customer data and for that reason has not been publicly available. The only publicly available part of our testing process consisted of the crash-me test, a Perl DBI/DBD benchmark found in the sql-bench directory, and miscellaneous tests located in tests directory. The lack of a standardized publicly available test suite has made it difficult for our users, as well developers, to do regression tests on the MySQL code. To address this problem, we have created a new test system that is included in the source and binary distributions starting in Version 3.23.29.

The current set of test cases doesn't test everything in MySQL but, it should catch most obvious bugs in the SQL processing code, OS/library issues, and is quite thorough in testing replication. Our eventual goal is to have the tests cover 100% of the code. We welcome contributions to our test suite. You may especially want to contribute tests that examine the functionality critical to your system, as this will ensure that all future MySQL releases will work well with your applications.

26.2.1 Running the MySQL Test Suite

The test system consist of a test language interpreter (mysqltest), a shell script to run all tests(mysql-test-run), the actual test cases written in a special test language, and their expected results. To run the test suite on your system after a build, type make test or mysql-test/mysql-test-run from the source root. If you have installed a binary distribution, cd to the install root (eg. /usr/local/mysql), and do scripts/mysql-test-run. All tests should succeed. If not, you should try to find out why and report the problem if this is a bug in MySQL. See section 26.2.3 Reporting bugs in the MySQL Test Suite.

If you have a copy of mysqld running on the machine where you want to run the test suite you do not have to stop it, as long as it is not using ports 9306 and 9307. If one of those ports is taken, you should edit mysql-test-run and change the values of the master and/or slave port to one that is available.

You can run one individual test case with mysql-test/mysql-test-run test_name.

If one test fails, you should test running mysql-test-run with the --force option to check if any other tests fails.

26.2.2 Extending the MySQL Test Suite

You can use the mysqltest language to write your own test cases. Unfortunately, we have not yet written full documentation for it - we plan to do this shortly. You can, however, look at our current test cases and use them as an example. The following points should help you get started:

26.2.3 Reporting bugs in the MySQL Test Suite

If your MySQL version doesn't pass the test suite you should do the following:

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