The MyRocks storage engine lacks the following features compared to InnoDB:
- Online DDL
- ALTER TABLE ... EXCHANGE PARTITION
- Transportable tablespace
- Foreign keys
- Spatial indexes
- Fulltext indexes
- Gap locks
- Group Replication
- Partial Update of LOB in InnoDB
You should also consider the following:
latin1_bin) or binary collation should be used on
VARCHARindexed columns. By default, MyRocks prevents creating indexes with non-binary collations (including
latin1). You can optionally use it by setting
t1(table names with regex format), but non-binary covering indexes other than
german1) still require a primary key lookup to return the
ORDER BY DESCor
ORDER BY ASCis slow. This is because of “Prefix Key Encoding” feature in RocksDB. See http://www.slideshare.net/matsunobu/myrocks-deep-dive/58 for details. By default, ascending scan is faster and descending scan is slower. If the “reverse column family” is configured, then descending scan will be faster and ascending scan will be slower. Note that InnoDB also imposes a cost when the index is scanned in the opposite order.
MyRocks does not support operating as either a master or a slave in any replication topology that is not exclusively row-based. Statement-based and mixed-format binary logging is not supported. For more information, see Replication Formats.
When converting from large MyISAM/InnoDB tables, either by using the
INSERT INTO SELECTstatements it’s recommended that you check the Data loading documentation and create MyRocks tables as below (in case the table is sufficiently big it will cause the server to consume all the memory and then be terminated by the OOM killer):
SET session sql_log_bin=0; SET session rocksdb_bulk_load=1; ALTER TABLE large_myisam_table ENGINE=RocksDB; SET session rocksdb_bulk_load=0; .. warning:: If you are loading large data without enabling :variable:`rocksdb_bulk_load` or :variable:`rocksdb_commit_in_the_middle`, please make sure transaction size is small enough. All modifications of the ongoing transactions are kept in memory.
The`XA protocol <https://dev.mysql.com/doc/refman/8.0/en/xa.html>`_ support, which allows distributed transactions combining multiple separate transactional resources, is an experimental feature in MyRocks: the implementation is less tested, it may lack some functionality and be not as stable as in case of InnoDB.
With partitioned tables that use the TokuDB or MyRocks storage engine, the upgrade only works with native partitioning.
- MySQL Documentation: Preparing Your Installation for Upgrade
Percona Server for MySQL 8.0 and Unicode 9.0.0 standards have defined a change in the handling of binary collations. These collations are handled as NO PAD, trailing spaces are included in key comparisons. A binary collation comparison may result in two unique rows inserted and does not generate a`DUP_ENTRY` error. MyRocks key encoding and comparison does not account for this character set attribute.
Percona Server for MySQL 8.0.16 does not support encryption for the MyRocks storage engine. At this time, during an
ALTER TABLEoperation, MyRocks mistakenly detects all InnoDB tables as encrypted. Therefore, any attempt to
ALTERan InnoDB table to MyRocks fails.
As a workaround, we recommend a manual move of the table. The following steps are the same as the
ALTER TABLE ... ENGINE=... process:
- Use ``SHOW CREATE TABLE ... `` to return the InnoDB table definition.
- With the table definition as the source, perform a
CREATE TABLE ... ENGINE=RocksDB.
- In the new table, use
INSERT INTO <new table> SELECT * FROM <old table>.
With MyRocks and with large tables, it is recommended to set the session variable
rocksdb_bulk_load=1during the load to prevent running out of memory. This recommendation is because of the MyRocks large transaction limitation.
MyRocks Data Loading https://www.percona.com/doc/percona-server/8.0/myrocks/data_loading.html