Differences Between MyRocks Variants

MyRocks is available in

• Facebook's (FB) MySQL branch (originally based on MySQL 5.6)

• MariaDB (from 10.2 and 10.3)

• Percona Server from 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 variable. From , algorithms can be . In earlier versions, the set of supported compression algorithms depends on the platform.

  • On Ubuntu 16.04 (current LTS) it is Snappy,Zlib,LZ4,LZ4HC .

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)

• MariaDB currently uses 5.8.0

• Percona Server uses 5.8.0

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:

• MariaDB doesn't include the Gap Lock Detector.

Generated Columns

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

• in are supported (as they are an SQL layer feature).

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

• (MyRocks is beta)

_{This page is licensed: CC BY-SA / Gnu FDL}