SkySQL has a MariaDB vs MySQL whitepaper available for download.
See also MariaDB vs MySQL - Features
- MariaDB is a binary drop in replacement for MySQL
- Incompatibilities between MariaDB 5.1 and MySQL 5.1
- Incompatibilities between MariaDB 5.2 and MySQL 5.1
- Incompatibilities between MariaDB 5.3 and MySQL 5.1 and MariaDB 5.2
- Incompatibilities between MariaDB 5.5 and MariaDB 5.3
- Incompatibilities between MariaDB 5.5 and MariaDB 5.3 and MySQL 5.5
- Incompatibilities between MariaDB 10.0 and MySQL 5.6
- Old, unsupported configuration options
- Replacing a MySQL RPM
- Incompatibilities between MariaDB and MySQL-Proxy
MariaDB is a binary drop in replacement for MySQL
For all practical purposes, MariaDB is a binary drop in replacement of the same MySQL version (for example MySQL 5.1 -> MariaDB 5.1, MariaDB 5.2 & MariaDB 5.3 are compatible. MySQL 5.5 will be compatible with MariaDB 5.5). What this means is that:
- Data and table definition files (.frm) files are binary compatible.
- All client APIs, protocols and structs are identical.
- All filenames, binaries, paths, ports, sockets, and etc... should be the same.
- All MySQL connectors (PHP, Perl, Python, Java, .NET, MyODBC, Ruby, MySQL C
connector etc) work unchanged with MariaDB.
- There are some installation issues with PHP5 that you should be aware of (a bug in how the old PHP5 client checks library compatibility).
mysql-clientpackage also works with MariaDB server.
- The shared client library is binary compatible with MySQL's client library.
This means that for most cases, you can just uninstall MySQL and
install MariaDB and you are good
to go. (No need to convert any datafiles if you use same main version, like
5.1). You must however still run
mysql_upgrade to finish the upgrade. This is needed to ensure that your mysql privilege and event tables are updated with the new fields MariaDB uses.
We do monthly merges with the MySQL code base to ensure we keep up our compatibility and get any and all features and bug fixes Oracle adds.
We have also done a lot of work on the upgrade scripts to the point where it is now easier to upgrade from MySQL 5.0 to MariaDB 5.1 than from MySQL 5.0 to MySQL 5.1.
That said, MariaDB has a lot of new options, extension, storage engines and bug fixes that are not in MySQL. You can find the feature set for the different MariaDB versions on the What is in the different MariaDB Releases page.
Incompatibilities between MariaDB 5.1 and MySQL 5.1
In some few cases MariaDB has to be incompatible to allow MariaDB to provide more and better information than MySQL.
Here is the list of all known user level incompatibilities you may see when using MariaDB 5.1 instead of MySQL 5.1.
- The installation package names start with MariaDB instead of MySQL.
- Timings may be different as MariaDB is in many cases faster than MySQL.
- mysqld in MariaDB also reads the
[mariadb]sections of your my.cnf files.
- You can't use a binary only storage engine library with MariaDB if it's not compiled for exactly the same MariaDB version. (This is because the server internal structure THD is different between MySQL and MariaDB. This is common also between different MySQL versions). This should not be a problem as most people don't load new storage engines and MariaDB comes with more storage engines than MySQL.
CHECKSUM TABLEmay give different result as MariaDB doesn't ignore NULL's in the columns as MySQL 5.1 does (Future MySQL versions should calculate checksums the same way as MariaDB). You can get the 'old style' checksum in MariaDB by starting mysqld with the
--oldoption. Note however that that the MyISAM and Aria storage engines in MariaDB are using the new checksum internally, so if you are using
CHECKSUMcommand will be slower as it needs to calculate the checksum row by row.
- The slow query log has more information about the query, which may be a problem if you have a script which parses the slow query log.
- MariaDB by default takes a bit more memory than MySQL because we have by
default enabled the Aria storage engine for
handling internal temporary tables. If you need MariaDB to take very little
memory (at the expense of performance), you can set the value
1M(the default is
- If you are using new command options, new features of MariaDB or new storage engines, you can't move easily back and forth between MySQL and MariaDB anymore.
Incompatibilities between MariaDB 5.2 and MySQL 5.1
The list is the same as between MariaDB 5.1 and MySQL 5.1, with one addition:
- A new SQL_MODE value was added:
IGNORE_BAD_TABLE_OPTIONS. If it is not set, using a table, field, or index attribute (option) that is not supported by the chosen storage engine will cause an error. This change might cause warnings in the error log about incorrectly defined tables from the
mysqldatabase, fix that with mysql_upgrade.
Incompatibilities between MariaDB 5.3 and MySQL 5.1 and MariaDB 5.2
- A few error messages related to wrong conversions are different as MariaDB provides more information in the message about what went wrong.
- Error numbers for MariaDB-specific errors have been moved to start from 1900 so as not to conflict with MySQL errors.
- Microseconds now work in all contexts; MySQL, in some contexts, lost the microsecond part from datetime and time.
- UNIX_TIMESTAMP(constant-date-string) returns a timestamp with 6 decimals in MariaDB while MySQL returns it without a decimal. This can cause a problem if you are using UNIX_TIMESTAMP() as a partitioning function. You can fix this by using FLOOR(UNIX_TIMESTAMP(..)) or changing the date string to a date number, like 20080101000000.
- MariaDB performs stricter checking of date, datetime and timestamp values. For example UNIX_TIMESTAMP('x') now returns NULL instead of 0.
- The old
--maria-startup options are removed. You should use the
--aria-prefix instead. (MariaDB 5.2 supports both
SHOW PROCESSLISThas an extra
Progresscolumn which shows progress for some commands. You can disable it by starting
--old-mode=NO_PROGRESS_INFOor with the
--oldflag (see OLD_MODE).
INFORMATION_SCHEMA.PROCESSLISThas three new columns for progress reporting:
- Long comments which start with
- If you use max_user_connections=0 (which means any number of connections) when starting mysqld, you can't change the global variable
anymore while mysqld remains running. This is because when mysqld is started
max_user_connections=0it does not allocate counting structures (which also involve a mutex for each connection). This would lead to wrong counters if you later changed the variable. If you want to be able to change this variable at runtime, set it to a high value at startup.
- You can set
max_user_connections(both the global variable and the
-1to stop users from connecting to the server. The global
max_user_connectionsvariable does not affect users with the
- The IGNORE directive does not ignore all errors (like fatal errors), only things that are safe to ignore.
Incompatibilities between MariaDB 5.5 and MariaDB 5.3
XtraDB options missing in 5.5
The following options are not supported by XtraDB 5.5. If you are using them in any of your my.cnf files, you should remove them before upgrading to 5.5.
- innodb_adaptive_checkpoint; Use innodb_adaptive_flushing_method instead.
- innodb_auto_lru_dump; Use innodb_buffer_pool_restore_at_startup instead (and innodb_buffer_pool_load_at_startup in MariaDB 10.0).
- innodb_blocking_lru_restore; Use innodb_blocking_buffer_pool_restore instead.
- innodb_expand_import; Use innodb_import_table_from_xtrabackup instead.
- innodb_extra_rsegments; Use innodb_rollback_segments instead.
- innodb_pass_corrupt_table; Use innodb_corrupt_table_action instead.
XtraDB options that have changed default value
New options in XtraDB 5.5
The following new options have been added to XtraDB / InnoDB in 5.5. (Listed here just to have all XtraDB information in the same place)
Incompatibilities between MariaDB 5.5 and MariaDB 5.3 and MySQL 5.5
- INSERT IGNORE also gives warnings for duplicate key errors. You can turn this off by setting
Incompatibilities between MariaDB 10.0 and MySQL 5.6
- All MySQL binaries (
mysqld, myisamchk etc.) give a warning if one uses a prefix of an option (such as
--big-tables). MariaDB binaries work in the same way as most other Unix commands and don't give warnings when using unique prefixes.
- MariaDB GTID is not compatible with MySQL 5.6. This means that one can't have MySQL 5.6 as a slave for MariaDB 10.0
- To make CREATE TABLE ... SELECT work the same way in statement based and row based replication it's by default executed as CREATE OR REPLACE TABLE on the slave. One benefit of this is that if the slave dies in the middle of CREATE ... SELECT it will be able to continue.
- One can use the slave-ddl-exec-mode variable to specify how
DROP TABLEis replicated.
- One can use the slave-ddl-exec-mode variable to specify how
Old, unsupported configuration options
If you are using any of the following options in your
/etc/my.cnf or other
my.cnf file you should remove them. This is also true for MySQL 5.1 or
Replacing a MySQL RPM
If you uninstalled a MySQL RPM to install MariaDB, note that the MySQL RPM on
After installing MariaDB you should do the following to restore your old configuration options:
mv -vi /etc/my.cnf.rpmsave /etc/my.cnf
Incompatibilities between MariaDB and MySQL-Proxy
A MySQL client API is able to connect to MariaDB using MySQL-Proxy but a MariaDB client API will receive progress reporting informations that MySQL-Proxy does not implement, to get full compatibility in all case just disable progress reporting on the client or server side.