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MariaDB server is a community developed fork of MySQL server. Started by core members of the original MySQL team, MariaDB actively works with outside developers to deliver the most featureful, stable, and sanely licensed open SQL server in the industry.
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Marko Mäkelä 1122ac978e MDEV-33545: Improve innodb_doublewrite to cover NO_FSYNC 
In commit 24648768b4 (MDEV-30136)
the parameter innodb_flush_method was deprecated, with no direct
replacement for innodb_flush_method=O_DIRECT_NO_FSYNC.

Let us change innodb_doublewrite from Boolean to ENUM that can
be changed while the server is running:

OFF: Assume that writes of innodb_page_size are atomic
ON: Prevent torn writes (the default)
fast: Like ON, but avoid synchronizing writes to data files

The deprecated start-up parameter innodb_flush_method=NO_FSYNC will cause
innodb_doublewrite=ON to be changed to innodb_doublewrite=fast,
which will prevent InnoDB from making any durable writes to data files.
This would normally be done right before the log checkpoint LSN is updated.
Depending on the file systems being used and their configuration,
this may or may not be safe.

The value innodb_doublewrite=fast differs from the previous combination of
innodb_doublewrite=ON and innodb_flush_method=O_DIRECT_NO_FSYNC by always
invoking os_file_flush() on the doublewrite buffer itself
in buf_dblwr_t::flush_buffered_writes_completed(). This should be safer
when there are multiple doublewrite batches between checkpoints.
Typically, once per second, buf_flush_page_cleaner() would write out
up to innodb_io_capacity pages and advance the log checkpoint.
Also typically, innodb_io_capacity>128, which is the size of the
doublewrite buffer in pages. Should os_file_flush_func() not be invoked
between doublewrite batches, writes could be reordered in an unsafe way.

The setting innodb_doublewrite=fast could be safe when the doublewrite
buffer (the first file of the system tablespace) and the data files
reside in the same file system.

This was tested by running "./mtr --rr innodb.alter_kill". On the first
server startup, with innodb_doublewrite=fast, os_file_flush_func()
would only be invoked on the ibdata1 file and possibly ib_logfile0.
On subsequent startups with innodb_doublewrite=OFF, os_file_flush_func()
will be invoked on the individual data files during log_checkpoint().

Note: The setting debug_no_sync (in the code, my_disable_sync) would
disable all durable writes to InnoDB files, which would be much less safe.

IORequest::Type: Introduce special values WRITE_DBL and PUNCH_DBL
for asynchronous writes that are submitted via the doublewrite buffer.
In this way, fil_space_t::use_doublewrite() or buf_dblwr.in_use()
will only be consulted during buf_page_t::flush() and the doublewrite
buffer can be enabled or disabled without any fear of inconsistency.

buf_dblwr_t::block_size: Replaces block_size().

buf_dblwr_t::flush_buffered_writes(): If !in_use() and the doublewrite
buffer is empty, just invoke fil_flush_file_spaces() and return. The
doublewrite buffer could have been disabled while a batch was in
progress.

innodb_init_params(): If innodb_flush_method=O_DIRECT_NO_FSYNC,
set innodb_doublewrite=fast or innodb_doublewrite=fearless.

Thanks to Mark Callaghan for reporting this, and Vladislav Vaintroub
for feedback.
2024-04-04 08:12:54 +03:00
.github Explicitly recommend target branches in CODING_STANDARDS 2023-12-14 16:32:42 +00:00
BUILD Merge branch '10.5' into 10.6 2023-12-17 11:20:43 +01:00
client Merge 10.11 into 11.0 2024-03-28 10:51:36 +02:00
cmake Merge 10.11 into 11.0 2024-03-28 10:51:36 +02:00
dbug Merge 10.6 into 10.8 2023-02-10 13:43:53 +02:00
debian Merge 10.5 into 10.6 2024-03-27 15:00:56 +02:00
Docs Fixed some typos in optimizer_costs.txt 2023-03-28 18:41:09 +11:00
extra MDEV-33545: Improve innodb_doublewrite to cover NO_FSYNC 2024-04-04 08:12:54 +03:00
include Merge 10.11 into 11.0 2024-03-28 10:51:36 +02:00
libmariadb@e714a67482 Return back wolfssl v5.6.6 and new CC changed by 6b2cd78695 2024-02-12 12:43:08 +01:00
libmysqld Merge 10.6 into 10.11 2024-03-28 09:16:57 +02:00
libservices Merge 10.6 into 10.11 2024-02-08 15:04:46 +02:00
man Merge 10.11 into 11.0 2024-02-20 12:02:01 +02:00
mysql-test MDEV-33545: Improve innodb_doublewrite to cover NO_FSYNC 2024-04-04 08:12:54 +03:00
mysys Merge 10.11 into 11.0 2024-03-28 10:51:36 +02:00
mysys_ssl Merge branch '10.4' into 10.5 2023-08-01 11:52:13 +02:00
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randgen/conf Group commit for maria engine. 2010-02-12 15:12:28 +02:00
scripts Merge 10.11 into 11.0 2024-03-28 10:51:36 +02:00
sql Merge 10.11 into 11.0 2024-03-28 10:51:36 +02:00
sql-bench Updated sql-bench to run with PostgreSQL 14.9 2023-09-09 15:14:45 +03:00
sql-common Merge branch '10.5' into 10.6 2023-12-17 11:20:43 +01:00
storage MDEV-33545: Improve innodb_doublewrite to cover NO_FSYNC 2024-04-04 08:12:54 +03:00
strings Merge branch '10.6' into 10.11 2024-02-01 18:36:14 +01:00
support-files Merge 10.6 into 10.11 2024-03-28 09:16:57 +02:00
tests Merge 10.11 into 11.0 2024-03-28 10:51:36 +02:00
tpool Merge 10.6 into 10.11 2023-11-22 18:14:11 +02:00
unittest Merge 10.6 into 10.11 2024-03-28 09:16:57 +02:00
vio Merge 10.6 into 10.11 2024-03-28 09:16:57 +02:00
win Merge branch '10.4' into 10.5 2024-01-31 17:32:53 +01:00
wsrep-lib@7d108eb870 galera: wsrep-lib submodule update 2024-03-25 12:13:57 +01:00
zlib Merge branch 'zlib v1.3' into 10.4 2023-10-18 20:39:48 +02:00
.clang-format Merge 10.4 into 10.5 2019-12-27 21:17:16 +02:00
.gitattributes Merge branch '10.5' into 10.6 2022-02-03 17:01:31 +01:00
.gitignore Merge branch '10.11' into 11.0 2023-09-29 12:24:54 +02:00
.gitlab-ci.yml Merge 10.11 into 11.0 2024-03-28 10:51:36 +02:00
.gitmodules Merge remote-tracking branch '10.4' into 10.5 2023-03-31 21:32:41 +02:00
appveyor.yml Merge 10.5 into 10.6 2022-07-27 17:52:37 +03:00
BUILD-CMAKE Minor spelling fixes in code comments, docs and output 2018-01-12 16:49:02 +02:00
CMakeLists.txt Merge 10.11 into 11.0 2023-10-19 08:12:16 +03:00
CODING_STANDARDS.md Explicitly recommend target branches in CODING_STANDARDS 2023-12-14 16:32:42 +00:00
config.h.cmake MDEV-33379 innodb_log_file_buffering=OFF causes corruption on bcachefs 2024-02-20 13:43:19 +02:00
configure.cmake MDEV-33379 innodb_log_file_buffering=OFF causes corruption on bcachefs 2024-02-20 13:43:19 +02:00
CONTRIBUTING.md Add CODING_STANDARDS.md file 2023-02-03 15:47:17 +11:00
COPYING Update FSF Address 2019-05-11 21:29:06 +03:00
CREDITS CREDITS: re-instate Tencent Cloud 2023-01-25 16:44:26 +11:00
INSTALL-SOURCE Update AskMonty and Atlassian references to MariaDB 2016-03-08 15:24:01 +02:00
INSTALL-WIN-SOURCE Update AskMonty and Atlassian references to MariaDB 2016-03-08 15:24:01 +02:00
KNOWN_BUGS.txt Changed some MySQL names in messages to MariaDB 2018-12-09 20:49:05 +02:00
README.md Remove mention of Freenode 2021-09-22 07:15:08 +02:00
THIRDPARTY Merge branch '10.6' into 10.11 2024-02-01 18:36:14 +01:00
VERSION bump the VERSION 2024-02-08 09:05:18 +01:00

README.md

Code status:

  • Appveyor CI status ci.appveyor.com

MariaDB: The open source relational database

MariaDB was designed as a drop-in replacement of MySQL(R) with more features, new storage engines, fewer bugs, and better performance.

MariaDB is brought to you by the MariaDB Foundation and the MariaDB Corporation. Please read the CREDITS file for details about the MariaDB Foundation, and who is developing MariaDB.

MariaDB is developed by many of the original developers of MySQL who now work for the MariaDB Corporation, the MariaDB Foundation and by many people in the community.

MySQL, which is the base of MariaDB, is a product and trademark of Oracle Corporation, Inc. For a list of developers and other contributors, see the Credits appendix. You can also run 'SHOW authors' to get a list of active contributors.

A description of the MariaDB project and a manual can be found at:

https://mariadb.org

https://mariadb.com/kb/en/

https://mariadb.com/kb/en/mariadb-vs-mysql-features/

https://mariadb.com/kb/en/mariadb-versus-mysql-compatibility/

https://mariadb.com/kb/en/new-and-old-releases/

Help

More help is available from the Maria Discuss mailing list https://launchpad.net/~maria-discuss, MariaDB's Zulip instance, https://mariadb.zulipchat.com/

Live QA for beginner contributors

MariaDB has a dedicated time each week when we answer new contributor questions live on Zulip. From 8:00 to 10:00 UTC on Mondays, and 10:00 to 12:00 UTC on Thursdays, anyone can ask any questions they’d like, and a live developer will be available to assist.

New contributors can ask questions any time, but we will provide immediate feedback during that interval.

Licensing

NOTE:

MariaDB is specifically available only under version 2 of the GNU General Public License (GPLv2). (I.e. Without the "any later version" clause.) This is inherited from MySQL. Please see the README file in the MySQL distribution for more information.

License information can be found in the COPYING file. Third party license information can be found in the THIRDPARTY file.

Bug Reports

Bug and/or error reports regarding MariaDB should be submitted at: https://jira.mariadb.org

For reporting security vulnerabilities see: https://mariadb.org/about/security-policy/

The code for MariaDB, including all revision history, can be found at: https://github.com/MariaDB/server