Fix a bunch of issues found with locking, ordering, and non-thread-safe stuff
in Relay_log_info.
Now able to do a simple benchmark, showing 4.5 times speedup for applying a
binlog with 10000 REPLACE statements.
Impement options --binlog-commit-wait-count and
--binlog-commit-wait-usec.
These options permit the DBA to deliberately increase latency
of an individual commit to get more transactions in each
binlog group commit. This increases the opportunity for
parallel replication on the slave, and can also decrease I/O
load on the master.
The options also make it easier to test the parallel
replication with mysql-test-run.
Fix some bugs around waiting for worker threads to end during SQL slave stop.
Free Log_event after parallel execution (still needs to be made thread-safe by
using rpl_group_info rather than rli).
Wait for all worker threads to finish when stopping the SQL thread.
(Only a basic wait; this still needs to be fixed to include timeout
logic as in sql_slave_killed()).
Hook in the wait-for-prior-commit logic (not really tested yet).
Clean up some resource maintenance around rpl_group_info (may still be some
smaller issues there though).
Add a ToDo list at the top of rpl_parallel.cc
