Looking at Rdb_binlog_manager in FB/MySQL.

Feature 1: store the master position in MyRocks

It stores the master position in this record:

key: BINLOG_INFO_INDEX_NUMBER

value:  

  - binlog_file:position

  - Last GTID (isn't that a function of binlog position?)

Uses for that information:

• It is printed to stderr on server startup (see rocksdb_recover()).
• It is used to move the binlog position forward during recovery:
  https://github.com/facebook/mysql-5.6/commit/00861dd66bf37c916558e57caff3875720beebb9
  (This targets the usecase with sync_binlog !=1 and innodb_flush_log_at_trx_commit !=1)

• It is visible through INFORMATION_SCHEMA.ROCKSDB_GLOBAL_INFO.

Re #2, InnoDB in FB/MySQL has similar code in is_binlog_advanced (and MariaDB's InnoDB doesn't have it)

Feature 2: keep mysql.slave_gtid_info up to date

When slave-gtid-info=optimized option is used, mysql.slave_gtid_info is kept up-todate directly by the storage engines. (See https://github.com/facebook/mysql-5.6/commit/0f402cb8381ba9d8e71c93085a22e5a12589b6e3)

(Q: and that option is not used, both the SE and the SQL layer do the updates?)

Proposed solution

• Neither of the above features are essential (or storage engine-only)
• MariaDB has an error when trying to use a part of Rdb_binlog_manager (as it doesn't have binlog position stored). We need to disable it.