Incompatibilities and Feature Differences Between MariaDB 10.5 and MySQL 8.0

The following is a list of incompatibilities and feature differences between MariaDB 10.5 and MySQL 8.0. It is based on the stable versions MySQL 8.0.22 and MariaDB 10.5.6. Note that MySQL 8 is an 'evergreen' release, so features may be added or removed in later releases.

Storage Engines

In addition to the standard InnoDB, MyISAM, BLACKHOLE, CSV, MEMORY, ARCHIVE, and MERGE storage engines, the following are also available with MariaDB 10.5:

  • ColumnStore utilizes a massively parallel distributed data architecture and is designed for big data scaling to process petabytes of data.
  • MyRocks, a storage engine with great compression
  • S3 storage engine allows one to archive MariaDB tables in Amazon S3, or any third-party public or private cloud that implements S3 API.
  • Aria, MyISAM replacement with better caching.
  • CONNECT
  • SEQUENCE
  • Spider
  • SphinxSE
  • FederatedX (drop-in replacement for Federated)
  • OQGRAPH

Extensions and New Features

The most notable features available in MariaDB, but not in MySQL, are:

Incompatibilities

When moving from MySQL 8.0 to MariaDB 10.5, please take note of the following incompatibilities:

  • For a list of function differences, see Function Differences Between MariaDB 10.5 and MySQL 8.0
  • For a list of system variable differences, see System Variable Differences Between MariaDB 10.5 and MySQL 8.0
  • MariaDB's GTID is not compatible with MySQL's. Note that MariaDB and MySQL also have different GTID system variables, so these need to be adjusted when migrating.
  • The unix_socket authentication plugin is now default on Unix-like systems, which is a major change to authentication in MariaDB. See Authentication from MariaDB 10.4 for an overview of the changes.
  • All mysql* binaries are now named mariadb* (the previous mysql named is retained as a symlink for compatibility purposes)
  • Not all character sets and collations are supported across both MySQL and MariaDB. As of 10.5.4, MariaDB supports 40 character sets and 322 collations. As of 8.0.21, MySQL supports 41 character sets and 272 collations.
  • 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 CREATE TABLE and DROP TABLE is replicated.
  • Users created with MySQL's SHA256 password algorithm cannot be used in MariaDB 10.5.
  • MariaDB stores JSON as true text, not in binary format as MySQL. MariaDB's JSON functions are much faster than MySQL's so there is no need to store in binary format, which would add complexity when manipulating JSON objects.
  • For the same reason, MariaDB's JSON data type is an alias for LONGTEXT. If you want to replicate JSON columns from MySQL to MariaDB, you should store JSON objects in MySQL in a TEXT or LONGTEXT column or use statement based replication. If you are using JSON columns and want to upgrade to MariaDB, you need to either convert them to TEXT or use mysqldump to copy these tables to MariaDB.
  • In MySQL, JSON is compared according to json values. In MariaDB JSON strings are normal strings and compared as strings.
  • MariaDB 10.5 does not support MySQL's JSON operators (-> and ->>).
  • MariaDB 10.5 supports the standard by producing null and a warning for JSON_SEARCH when given invalid data, while MySQL produces an error.
  • Roles
    • MariaDB never allows authentication via roles, while MySQL permits this.
    • MySQL permits activating multiple roles at the same time. MariaDB can achieve the same result by creating an intermediate aggregate role.
    • In the INFORMATION_SCHEMA.ENABLED_ROLES table, MySQL reports just the direct list of enabled roles, while MariaDB reports the enabled role, plus the effective inherited roles.
    • MySQL extends the INFORMATION_SCHEMA.APPLICABLE_ROLES table .
    • MySQL includes the tables INFORMATION_SCHEMA.ROLE_TABLE_GRANTS, INFORMATION_SCHEMA.ROLE_ROUTINE_GRANTS, INFORMATION_SCHEMA.ROLE_COLUMN_GRANTS, and INFORMATION_SCHEMA ADMINISTRABLE_ROLE_AUTHORIZATIONS.
  • MySQL has the performance schema enabled by default. For performance reasons MariaDB 10.5 has it disabled by default. You can enable it by starting mysqld with the option --performance-schema.
  • In MariaDB 10.4, using FLUSH TABLES without any table list will only close tables not in use, and tables not locked by the FLUSH TABLES connection. If there are no locked tables, FLUSH TABLES will be instant and will not cause any waits, as it no longer waits for tables in use. When a table list is provided, the server will wait for the end of any transactions that are using the tables. In MySQL, FLUSH TABLES only waits for the statements to complete.
  • MariaDB binaries (mysqld, myisamchk etc.) give a warning if one uses a unique prefix of an option (such as --big-table instead of --big-tables). MySQL binaries require the full option name.
  • MariaDB 10.5 implements InnoDB encryption in a different way to MySQL 8.0.
  • MySQL's implementation of aborting statements that exceed a certain time to execute can only kill SELECTs, while MariaDB's can kill any queries (excluding stored procedures).
  • MariaDB 10.5 does not support MySQL's SELECT /*+ MAX_EXECUTION_TIME(n) */ ... - see Aborting Statements that Exceed a Certain Time to Execute.
  • MySQL 8.0 does not support the Query Cache.
  • MariaDB 10.5 does not support the MySQL Memcached plugin (which has been deprecated in MySQL 8.0). However, data stored using memcached can be retrieved because the data is stored as InnoDB tables. MariaDB is able to start successfully with an error message of not being able to find libmemcached.so library.
  • In MySQL, X'HHHH', the standard SQL syntax for binary string literals, erroneously works in the same way as 0xHHHH, which could work as a number or string depending on the context. In MariaDB, this has been fixed to behave as a string in all contexts (and never as a number). See CAST and Hexadecimal Literals for more details and examples.
  • In MariaDB 10.5, SHOW CREATE TABLE does not quote the DEFAULT value of an integer. MariaDB 10.2 and earlier, and MySQL, do. Since MariaDB can support defaults for BLOB and TEXT fields, while MySQL does not, SHOW CREATE TABLE will also append DEFAULT NULL where no default is explicitly provided to nullable BLOB or TEXT fields in MariaDB.
  • Since MariaDB supports INTERSECT and EXCEPT, these are both reserved words and can't be used as an identifier without being quoted.
  • As a result of implementing Table Value Constructors, the VALUES function has been renamed to VALUE().
  • MariaDB does not support the --initialize option. Use mysql_install_db instead. - MDEV-19010
  • MariaDB 10.5 does not support the ngram and MeCab full-text parser plugins - MDEV-10267, MDEV-10268.
  • MariaDB 10.5 does not support the MySQL X plugin.
  • MariaDB 10.5 does not support MySQL 8's “native” InnoDB partitioning handler.
  • MariaDB 10.5 does not support CREATE TABLESPACE for InnoDB.
  • The MySQL 8.0 and MariaDB 10.5 INFORMATION_SCHEMA.COLUMNS table contain slightly different fields.

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