MDEV-6676: Optimistic parallel replication

Adjust the configuration options, as discussed on the
maria-developers@ mailing list.

The option to hint a transaction to not be replicated in parallel is
now called @@skip_parallel_replication, consistent with
@@skip_replication.

And the --slave-parallel-mode is now simplified to have just one of
the following values:

  none
  minimal
  conservative
  optimistic
  aggressive

This reflects successively harder efforts to find opportunities to run
things in parallel on the slave. It allows to extend the server with
more automatic heuristics in the future without having to introduce a
new configuration option for each and every one.

1 files changed, 9 insertions, 10 deletions

diff --git a/mysql-test/r/mysqld--help.result b/mysql-test/r/mysqld--help.result
index bcda25c5f9b..dc2f2b3d270 100644
--- a/mysql-test/r/mysqld--help.result
+++ b/mysql-test/r/mysqld--help.result
@@ -922,15 +922,14 @@ The following options may be given as the first argument:
  replication. Only used when --slave-parallel-threads > 0.
  --slave-parallel-mode=name 
  Controls what transactions are applied in parallel when
- using --slave-parallel-threads. Syntax:
- slave_parallel_mode=value[,value...], where "value" could
- be one or more of: "domain", to apply different
- replication domains in parallel; "follow_master_commit",
- to apply in parallel transactions that group-committed
- together on the master; "transactional", to
- optimistically try to apply all transactional DML in
- parallel; and "waiting" to extend "transactional" to even
- transactions that had to wait on the master.
+ using --slave-parallel-threads. Possible values:
+ "optimistic" tries to apply most transactional DML in
+ parallel, and handles any conflicts with rollback and
+ retry. "conservative" limits parallelism in an effort to
+ avoid any conflicts. "aggressive" tries to maximise the
+ parallelism, possibly at the cost of increased conflict
+ rate. "minimal" only parallelizes the commit steps of
+ transactions. "none" disables parallel apply completely.
  --slave-parallel-threads=# 
  If non-zero, number of threads to spawn to apply in
  parallel events on the slave that were group-committed on
@@ -1351,7 +1350,7 @@ slave-exec-mode STRICT
 slave-max-allowed-packet 1073741824
 slave-net-timeout 3600
 slave-parallel-max-queued 131072
-slave-parallel-mode domain,follow_master_commit
+slave-parallel-mode conservative
 slave-parallel-threads 0
 slave-run-triggers-for-rbr NO
 slave-skip-errors (No default value)