MyRocks Limitations¶
The MyRocks storage engine lacks the following features compared to InnoDB:
- Online DDL is not supported due to the lack of atomic DDL support.
- There is no
ALTER TABLE ... ALGORITHM=INSTANT
functionality- A partition management operation only supports the
COPY
algorithms, which rebuilds the partition table and moves the data based on the newPARTITION ... VALUE
definition. In the case ofDROP PARTITION
, the data not moved to another partition is deleted.- ALTER TABLE .. EXCHANGE PARTITION.
- SAVEPOINT
- Transportable tablespace
- Foreign keys
- Spatial indexes
- Fulltext indexes
- Gap locks
- Generated Columns
- Group Replication
- Partial Update of LOB in InnoDB
You should also consider the following:
*_bin
(e.g.latin1_bin
) or binary collation should be used onCHAR
andVARCHAR
indexed columns. By default, MyRocks prevents creating indexes with non-binary collations (includinglatin1
). You can optionally use it by settingrocksdb_strict_collation_exceptions
tot1
(table names with regex format), but non-binary covering indexes other thanlatin1
(excludinggerman1
) still require a primary key lookup to return theCHAR
orVARCHAR
column.Either
ORDER BY DESC
orORDER BY ASC
is 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 source or a replica 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.
As of 8.0.17, InnoDB supports multi-valued indexes. MyRocks does not support this feature.
As of 8.0.17, InnoDB supports the use of the Clone Plugin and the Clone Plugin API. MyRocks tables do not support either these features.
When converting from large MyISAM/InnoDB tables, either by using the
ALTER
orINSERT INTO SELECT
statements 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.
With partitioned tables that use the TokuDB or MyRocks storage engine, the upgrade only works with native partitioning.
See also
- MySQL Documentation: Preparing Your Installation for Upgrade
https://dev.mysql.com/doc/refman/8.0/en/upgrade-prerequisites.html
The MyRocks storage engine does not support the
NO WAIT
andSKIP LOCKED
modifiers introduced in the InnoDB storage engine with MySQL 8.0.
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.
In version 8.0.13-3 and later, MyRocks does not support explicit DEFAULT value expressions.
Percona Server for MySQL 8.0.16 does not support encryption for the MyRocks storage engine. At this time, during an
ALTER TABLE
operation, MyRocks mistakenly detects all InnoDB tables as encrypted. Therefore, any attempt toALTER
an 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>
.Note
With MyRocks and with large tables, it is recommended to set the session variable
rocksdb_bulk_load=1
during the load to prevent running out of memory. This recommendation is because of the MyRocks large transaction limitation.See also
MyRocks Data Loading https://www.percona.com/doc/percona-server/8.0/myrocks/data_loading.html
MySQL has spatial data types . These data types are not supported by MyRocks.
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