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We will remove the InnoDB background operation of merging buffered changes to secondary index leaf pages. Changes will only be merged as a result of an operation that accesses a secondary index leaf page, such as a SQL statement that performs a lookup via that index, or is modifying the index. Also ROLLBACK and some background operations, such as purging the history of committed transactions, or computing index cardinality statistics, can cause change buffer merge. Encryption key rotation will not perform change buffer merge. The motivation of this change is to simplify the I/O logic and to allow crash recovery to happen in the background (MDEV-14481). We also hope that this will reduce the number of "mystery" crashes due to corrupted data. Because change buffer merge will typically take place as a result of executing SQL statements, there should be a clearer connection between the crash and the SQL statements that were executed when the server crashed. In many cases, a slight performance improvement was observed. This is joint work with Thirunarayanan Balathandayuthapani and was tested by Axel Schwenke and Matthias Leich. The InnoDB monitor counter innodb_ibuf_merge_usec will be removed. On slow shutdown (innodb_fast_shutdown=0), we will continue to merge all buffered changes (and purge all undo log history). Two InnoDB configuration parameters will be changed as follows: innodb_disable_background_merge: Removed. This parameter existed only in debug builds. All change buffer merges will use synchronous reads. innodb_force_recovery will be changed as follows: * innodb_force_recovery=4 will be the same as innodb_force_recovery=3 (the change buffer merge cannot be disabled; it can only happen as a result of an operation that accesses a secondary index leaf page). The option used to be capable of corrupting secondary index leaf pages. Now that capability is removed, and innodb_force_recovery=4 becomes 'safe'. * innodb_force_recovery=5 (which essentially hard-wires SET GLOBAL TRANSACTION ISOLATION LEVEL READ UNCOMMITTED) becomes safe to use. Bogus data can be returned to SQL, but persistent InnoDB data files will not be corrupted further. * innodb_force_recovery=6 (ignore the redo log files) will be the only option that can potentially cause persistent corruption of InnoDB data files. Code changes: buf_page_t::ibuf_exist: New flag, to indicate whether buffered changes exist for a buffer pool page. Pages with pending changes can be returned by buf_page_get_gen(). Previously, the changes were always merged inside buf_page_get_gen() if needed. ibuf_page_exists(const buf_page_t&): Check if a buffered changes exist for an X-latched or read-fixed page. buf_page_get_gen(): Add the parameter allow_ibuf_merge=false. All callers that know that they may be accessing a secondary index leaf page must pass this parameter as allow_ibuf_merge=true, unless it does not matter for that caller whether all buffered changes have been applied. Assert that whenever allow_ibuf_merge holds, the page actually is a leaf page. Attempt change buffer merge only to secondary B-tree index leaf pages. btr_block_get(): Add parameter 'bool merge'. All callers of btr_block_get() should know whether the page could be a secondary index leaf page. If it is not, we should avoid consulting the change buffer bitmap to even consider a merge. This is the main interface to requesting index pages from the buffer pool. ibuf_merge_or_delete_for_page(), recv_recover_page(): Replace buf_page_get_known_nowait() with much simpler logic, because it is now guaranteed that that the block is x-latched or read-fixed. mlog_init_t::mark_ibuf_exist(): Renamed from mlog_init_t::ibuf_merge(). On crash recovery, we will no longer merge any buffered changes for the pages that we read into the buffer pool during the last batch of applying log records. buf_page_get_gen_known_nowait(), BUF_MAKE_YOUNG, BUF_KEEP_OLD: Remove. btr_search_guess_on_hash(): Merge buf_page_get_gen_known_nowait() to its only remaining caller. buf_page_make_young_if_needed(): Define as an inline function. Add the parameter buf_pool. buf_page_peek_if_young(), buf_page_peek_if_too_old(): Add the parameter buf_pool. fil_space_validate_for_mtr_commit(): Remove a bogus comment about background merge of the change buffer. btr_cur_open_at_rnd_pos_func(), btr_cur_search_to_nth_level_func(), btr_cur_open_at_index_side_func(): Use narrower data types and scopes. ibuf_read_merge_pages(): Replaces buf_read_ibuf_merge_pages(). Merge the change buffer by invoking buf_page_get_gen().
This directory contains test suites for the MariaDB server. To run currently existing test cases, execute ./mysql-test-run in this directory. Some tests are known to fail on some platforms or be otherwise unreliable. The file "unstable-tests" contains the list of such tests along with a comment for every test. To exclude them from the test run, execute # ./mysql-test-run --skip-test-list=unstable-tests In general you do not have to have to do "make install", and you can have a co-existing MariaDB installation, the tests will not conflict with it. To run the tests in a source directory, you must do "make" first. In Red Hat distributions, you should run the script as user "mysql". The user is created with nologin shell, so the best bet is something like # su - # cd /usr/share/mysql-test # su -s /bin/bash mysql -c "./mysql-test-run --skip-test-list=unstable-tests" This will use the installed MariaDB executables, but will run a private copy of the server process (using data files within /usr/share/mysql-test), so you need not start the mysqld service beforehand. You can omit --skip-test-list option if you want to check whether the listed failures occur for you. To clean up afterwards, remove the created "var" subdirectory, e.g. # su -s /bin/bash - mysql -c "rm -rf /usr/share/mysql-test/var" If one or more tests fail on your system on reasons other than listed in lists of unstable tests, please read the following manual section for instructions on how to report the problem: https://mariadb.com/kb/en/reporting-bugs 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, you are expected to provide 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 socket=/tmp/mysql.sock alias analyze To match your setup, you might need to provide other relevant options. With no test names on the command line, mysql-test-run will attempt to execute the default set of tests, which will certainly fail, because many tests cannot run with an external server (they need to control the options with which the server is started, restart the server during execution, etc.) You can create your own test cases. To create a test case, create a new file in the main 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. 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 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 case consisting of SQL statements and comments, you can create the result file 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 --database test --result-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. If you want to submit your test case you can send it to maria-developers@lists.launchpad.net or attach it to a bug report on http://mariadb.org/jira/. If the test case is really big or if it contains 'not public' data, then 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://ftp.askmonty.org/private and submit a report to http://mariadb.org/jira about it. The latest information about mysql-test-run can be found at: https://mariadb.com/kb/en/mariadb/mysqltest/ If you want to create .rdiff files, check https://mariadb.com/kb/en/mariadb/mysql-test-auxiliary-files/