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.
Find a file
Nikita Malyavin ab4bfad206 MDEV-16329 [5/5] ALTER ONLINE TABLE
* Log rows in online_alter_binlog.
* Table online data is replicated within dedicated binlog file
* Cached data is written on commit.
* Versioning is fully supported.
* Works both wit and without binlog enabled.

* For now savepoints setup is forbidden while ONLINE ALTER goes on.
  Extra support is required. We can simply log the SAVEPOINT query events
  and replicate them together with row events. But it's not implemented
  for now.

* Cache flipping:

  We want to care for the possible bottleneck in the online alter binlog
  reading/writing in advance.

  IO_CACHE does not provide anything better that sequential access,
  besides, only a single write is mutex-protected, which is not suitable,
  since we should write a transaction atomically.

  To solve this, a special layer on top Event_log is implemented.
  There are two IO_CACHE files underneath: one for reading, and one for
  writing.

  Once the read cache is empty, an exclusive lock is acquired (we can wait
  for a currently active transaction finish writing), and flip() is emitted,
  i.e. the write cache is reopened for read, and the read cache is emptied,
  and reopened for writing.

  This reminds a buffer flip that happens in accelerated graphics
  (DirectX/OpenGL/etc).

  Cache_flip_event_log is considered non-blocking for a single reader and a
  single writer in this sense, with the only lock held by reader during flip.

  An alternative approach by implementing a fair concurrent circular buffer
  is described in MDEV-24676.

* Cache managers:
  We have two cache sinks: statement and transactional.
  It is important that the changes are first cached per-statement and
  per-transaction.
  If a statement fails, then only statement data is rolled back. The
  transaction moves along, however.

  Turns out, there's no guarantee that TABLE well persist in
  thd->open_tables to the transaction commit moment.
  If an error occurs, tables from statement are purged.
  Therefore, we can't store te caches in TABLE. Ideally, it should be
  handlerton, but we cut the corner and store it in THD in a list.
2023-08-15 10:16:11 +02:00
.github
BUILD
client
cmake
dbug
debian
Docs
extra
include
libmariadb@5af90f00ff
libmysqld
libservices
man
mysql-test
mysys
mysys_ssl
plugin
randgen/conf
scripts
sql
sql-bench
sql-common
storage
strings
support-files
tests MDEV-16329 [5/5] ALTER ONLINE TABLE 2023-08-15 10:16:11 +02:00
tpool
unittest
vio
win
wsrep-lib@e238c0d240
zlib
.clang-format
.gitattributes
.gitignore
.gitlab-ci.yml
.gitmodules
appveyor.yml
BUILD-CMAKE
CMakeLists.txt
CODING_STANDARDS.md
config.h.cmake
configure.cmake
CONTRIBUTING.md
COPYING
CREDITS
INSTALL-SOURCE
INSTALL-WIN-SOURCE
KNOWN_BUGS.txt
README.md
SECURITY.md
THIRDPARTY
VERSION

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 theyd 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 our security-policy.

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