The Ultimate Guide to High Availability with MariaDB

Differences between MyRocks variants

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MyRocks is available in

  • Facebook's 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.

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 libraries

  • FB's branch doesn't provide binaries. One needs to compile it with appropriate compression libraries.
  • MariaDB supports ... . Available compression libraries can be seen in @@rocksdb_supported_compression_types variable.

RocksDB version

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

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: One can take the output of myrocks_hotbackup and make it a new master.

Gap Lock Checking

Percona Server has gap lock checking ON by default. Queries that use Gap Lock will fail with an error:

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

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)

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