support binlog + rocksdb group commit and XA about mysql-5.6

[yoshinorim]

XA means XA between binlog and MyRocks -- writing xid into MyRocks, and proper roll forward/rollback at crash recovery.

[mdcallag]

This shows the impact (perf loss) from not having group commit in MyRocks.

This is the insert rate from a short run of the insert benchmark -- insert only, 3 secondary indexes/table, 10 clients each loading into a separate table, 10M rows total inserted using FB MySQL 5.6 with MyRocks vs Percona Server 5.6.26 for Toku. The database log (MyRocks, Toku) was not sync'ed on commit.

The database is on a 6 disk array with HW RAID and battery backed write cache.

Summary:

• MyRocks loses perf from not having group commit
• Toku in Percona Server no longer has a fast path when unique checks are disabled

Legend:

• sync=1 - binlog enabled, sync_binlog=1
• sync=0 - binlog enabled, sync_binlog=0
• nobl - binlog disabled
• nobl, nocheck - binlog disabled, unique checks disabled

inserts/second
rocks   toku    config
63694   129870  sync=1
64935   133333  sync=0
151515  136986  nobl
204082  136986  nobl, nocheck

[reidHoruff]

XA and group commit support had been added to MyRocks.