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 「4.8 開発ソースツリーからのインストール」節参照. 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

MySQL サーバーは以下のスレッドを作成します：

• TCP/IP 接続ハンドルは、全ての接続要求を扱い、さらに、 認証を行うためのスレッドSQLクエリを処理するスレッドを生成します
• Windows NTでは、名前付きパイプ(named pipe)・ハンドラー・スレッドがあります。 これはネームド・パイプの接続要求に対し、TCP/IP接続スレッドと同様に動きます。
• シグナルスレッドは、全てのシグナルを扱います。 This thread also normally handles alarms and calls process_alarm() to force timeouts on connections that have been idle too long.
• If mysqld is compiled with -DUSE_ALARM_THREAD, a dedicated thread that handles alarms is created. This is only used on some systems where there are problems with sigwait() or if one wants to use the thr_alarm() code in ones application without a dedicated signal handling thread.
• もし --flush-time=# オプションを使用したなら、 全てのテーブルを一定期間でフラッシュするためだけのスレッドを作ります。
• Every connection has its own thread.
• Every different table on which one uses INSERT DELAYED gets its own thread.
• If you use --master-host, a slave replication thread will be started to read and apply updates from the master.

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

mysqladmin processlist only shows the connection and INSERT DELAYED 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 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 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 they do not, use mysqlbug to send a bug report to bugs@lists.mysql.com. Make sure to include the output of mysql-test-run, as well as contents of all .reject files in mysql-test/r directory.

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.

The current set of test cases is far from comprehensive, as we have not yet converted all of our private tests to the new format. However, it should already 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.

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:

• The tests are located in mysql-test/t/*.test
• You can run one individual test case with mysql-test/mysql-test-run test_name removing .test extension from the file name
• A test case consists of ; terminated statements and is similar to the input of mysql command line client. A statement by default is a query to be sent to MySQL server, unless it is recognized as internal command ( eg. sleep ).
• All queries that produce results, e.g. SELECT, SHOW, EXPLAIN, etc., must be preceded with @/path/to/result/file. The file must contain the expected results. An easy way to generate the result file is to run mysqltest -r < t/test-case-name.test from mysql-test directory, and then edit the generated result files, if needed, to adjust them to the expected output. In that case, be very careful about not adding or deleting any invisible characters - make sure to only change the text and/or delete lines. If you have to insert a line, make sure the fields are separated with a hard tab, and there is a hard tab at the end. You may want to use od -c to make sure your text editor has not messed anything up during edit. We, of course, hope that you will never have to edit the output of mysqltest -r as you only have to do it when you find a bug.
• To be consistent with our setup, you should put your result files in mysql-test/r directory and name them test_name.result. If the test produces more than one result, you should use test_name.a.result, test_name.b.result, etc.
• Failed test results are put in a file with the same base name as the result file with the .reject extension. If your test case is failing, you should do a diff on the two files. If you cannot see how they are different, examine both with od -c and also check their lengths.
• You can prefix a query with ! if the test can continue after that query returns an error.
• If you are writing a replication test case, you should on the first line of the test file, put source include/master-slave.inc;. To switch between master and slave, use connection master; and connection slave;. If you need to do something on an alternate connection, you can do connection master1; for the master, and connection slave1; for the slave.
• If you need to do something in a loop, you can use something like this:

  let $1=1000;
  while ($1)
  {
   # do your queries here
   dec $1;
  }
  

• To sleep between queries, use the sleep command. It supports fractions of a second, so you can do sleep 1.3;, for example, to sleep 1.3 seconds.
• To run the slave with additional options for your test case, put them in the command-line format in mysql-test/t/test_name-slave.opt. For the master, put them in mysql-test/t/test_name-master.opt.
• If you have a question about the test suite, or have a test case to contribute, e-mail to internals@lists.mysql.com. As the list does not accept attachments, you should ftp all the relevant files to: ftp://support.mysql.com/pub/mysql/Incoming

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

• Don't send a bug report before you have found out as much as possible of what when wrong! When you do it, please use the mysqlbug script so that we can get information about your system and MySQL version. 「2.3 バグや問題を報告する方法」節参照.
• If you have compiled MySQL yourself, check our manual for how to compile MySQL on your platform or, preferable, use one of the binaries we have compiled for you at http://www.mysql.com/downloads/. All our standard binaries should pass the test suite !
• If you get an error, like Result length mismatch or Result content mismatch it means that the output of the test didn't match exactly the expected output. This could be a bug in MySQL or that your mysqld version produces slight different results under some circumstances. In this case you should compare the .test and .reject file in the mysql-test/r sub directory to see if this is something to worry about.
• If a test fails totally, you should check the logs file in the mysql-test/var/log directory for hints of what went wrong.
• If you have compiled MySQL with debugging you can try to debug this with the --gdb and --debug options to mysql-test-run. 「I.1.2 Creating trace files and using gdb on mysqld」節参照. If you have not compiled MySQL for debugging you should probably do that. Just specify the --with-debug options to configure! 「4.7 MySQL ソースディストリビューションのインストール」節参照.

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