On Tue, Dec 08, 2009 at 11:23:00AM -0500, Jay Pipes wrote: > >While I am no fan of a silent COMMIT, it may be the best solution, > >because at least this sequence of statements will be compatible > >with engines that support DDL in transactions and those that don't > >(much like MyISAM happily ignores BEGIN TRANSACTION). > > > >The alternative would be to return an error. This would prevent > >the surprise affect that I get when the server crashes and I > >discover my transaction was not atomic after all. > > Well, I'm not a huge fan of implicit anything, as you know, but in > this case, since engines do have a certain leeway in how they advise > the kernel that they will handle a statement, I'm OK with continuing > the existing MySQL behaviour of implicitly committing transactions > before DDL statements are executed -- but in Drizzle's case, only if > the engine advises it is unable to include the DDL in the current > transaction.
My choice would be to disallow the DDL if the engine involved can't cope with it being transactional (currently all). Probably will catch a lot of bugs in user applications. > Suppose PBXT can handle ADD INDEX in an optimized fashion, but PBXT > does not implement the remainder of the ALTER TABLE statement and > prefers Drizzle's kernel to handle the other operations. In this > particular case, we need a way of allowing the engine to communicate > that it would like to handle *some part* of a statement internally, > and let the kernel handle other parts. This is an interesting > problem, and I can see at least three possible solutions. Let me > know what you think of either of these: I like "EXPLAIN ALTER TABLE" :) along with ALTER TABLE ONLINE/OFFLINE syntax (already in mysql), this should work for all situations: - never implicit commit - allow offline operations (how it is now. also allows you to force it) - can find out if the ALTER you want to do can be done online (and what parts of it can) - can say "only do this if you can do it online" -- Stewart Smith _______________________________________________ Mailing list: https://launchpad.net/~drizzle-discuss Post to : [email protected] Unsubscribe : https://launchpad.net/~drizzle-discuss More help : https://help.launchpad.net/ListHelp
