consistency check support by total order isolation

[Seppo Jaakola]

Add support for consistency checking by reusing total order isolation semantics

[Seppo Jaakola (seppo-jaakola)]

In the first stage, consistency check should be enabled for INSERT...SELECT statements, which are marked by a special comment tag.
However, comment tagging is not simple anymore after MySQL client library is currently filtering comments out. We have some options to provide a workaround for this:
1. provide our own client library
2. completely new SQL syntax for CC
3. declaring CC state by session variable(s)
4. reusing conditional version comment /*!##### structure by piggy bagging WSREP syntax inside
    4A. reserving one magic version number directly for declaring CC state
    4B using magic WSREP version number to declare following comment contents as special WSREP language

Out of these alternatives, for the sake of simplicity, we should use #4A for the first implementation. Then consistency check can be triggered simply by a statement like:

INSERT...SELECT /*!99997*/

The magic CC version number here is 99997. MySQL client library should let that through and current server editions should filter it out

[Seppo Jaakola (seppo-jaakola)]

first implementation pushed in wsrep-5.5: http://bazaar.launchpad.net/~codership/codership-mysql/wsrep-5.5/revision/3719