W3cubDocs

/MariaDB

Differences Between MyRocks Variants

MyRocks is available in

  • Facebook's (FB) MySQL branch (based on MySQL 5.6, upcoming 8.0)
  • MariaDB (10.2 and 10.3)
  • Percona Server 5.7

This page lists differences between these variants.

This is a work in progress. The contents are not final

RocksDB Data Location

FB and Percona store RocksdDB files in $datadir/.rocksdb. MariaDB puts them in $datadir/#rocksdb. This is more friendly for packaging and OS scripts.

Compression Algorithms

  • FB's branch doesn't provide binaries. One needs to compile it with appropriate compression libraries.
  • In MariaDB, available compression algorithms can be seen in the rocksdb_supported_compression_types variable. The set of supported compression algorithms depends on the platform.
    • On Ubuntu 16.04 (current LTS) it is Snappy,Zlib,LZ4,LZ4HC .
    • On CentOS 7.4 it is Snappy,Zlib.
    • In the bintar tarball it is Snappy,Zlib.
  • Percona Server supports: Zlib, ZSTD, LZ4 (the default), LZ4HC. Unsupported algorithms: Snappy, BZip2, XPress.

RocksDB Version Information

  • FB's branch provides the rocksdb_git_hash *status* variable.
  • MariaDB provides the @@rocksdb_git_hash *system* variable.
  • Percona Server doesn't provide either.

RocksDB Version

  • Facebook's branch uses RocksDB 5.10.0 (the version number can be found in include/rocksdb/version.h)
commit ba295cda29daee3ffe58549542804efdfd969784
Author: Andrew Kryczka <[email protected]>
Date:   Fri Jan 12 11:03:55 2018 -0800
  • MariaDB currently uses 5.8.0
commit 9a970c81af9807071bd690f4c808c5045866291a
Author: Yi Wu <[email protected]>
Date:   Wed Sep 13 17:21:35 2017 -0700
  • Percona Server uses 5.8.0
commit ab0542f5ec6e7c7e405267eaa2e2a603a77d570b
Author: Maysam Yabandeh <[email protected]>
Date:   Fri Sep 29 07:55:22 2017 -0700

Binlog Position in information_schema.rocksdb_global_info

  • FB branch provides information_schema.rocksdb_global_info type=BINLOG, NAME={FILE, POS, GTID}.
  • Percona Server doesn't provide it.
  • MariaDB doesn't provide it.

One use of that information is to take the output of myrocks_hotbackup and make it a new master.

Gap Lock Detector

  • FB branch has a "Gap Lock Detector" feature. It is at the SQL layer. It can be controlled with gap_lock_XXX variables and is disabled by default (gap-lock-raise-error=false, gap-lock-write-lock=false).
  • Percona Server has gap lock checking ON but doesn't seem to have any way to control it? Queries that use Gap Lock on MyRocks fail with an error like this:
mysql> insert into tbl2 select * from tbl1;
ERROR 1105 (HY000): Using Gap Lock without full unique key in multi-table or multi-statement transactions
is not allowed. You need to either rewrite queries to use all unique key columns in WHERE equal conditions,
or rewrite to single-table, single-statement transaction.  Query: insert into tbl2 select * from tbl1
  • MariaDB doesn't include the Gap Lock Detector.

Generated Columns

  • Both MariaDB and Percona Server support generated columns, but neither one supports them for the MyRocks storage engine (attempts to create a table will produce an error).

rpl_skip_tx_api

Facebook's branch has a performance feature for replication slaves, rpl_skip_tx_api. It is not available in MariaDB or in Percona Server.

Details

The above comparison was made using

  • FB/MySQL 5.6.35
  • Percona Server 5.7.20-19-log
  • MariaDB 10.2.13 (MyRocks is beta)
Content reproduced on this site is the property of its respective owners, and this content is not reviewed in advance by MariaDB. The views, information and opinions expressed by this content do not necessarily represent those of MariaDB or any other party.

© 2019 MariaDB
Licensed under the Creative Commons Attribution 3.0 Unported License and the GNU Free Documentation License.
https://mariadb.com/kb/en/differences-between-myrocks-variants/