On Jul 23, 2009, at 3:15 PM, Stewart Smith wrote:
On Tue, Jul 21, 2009 at 09:28:54PM -0700, MARK CALLAGHAN wrote:
How is the serial log to be kept in sync with a storage engine given
the Applier interface? MySQL uses two phase commit, but the Applier
interface has one method, ::apply(). In addition to methods for
performing 2PC, keeping a storage engine and the serial log in sync
requires additional methods for crash recovery to support commit or
rollback of transactions in state PREPARED in the storage engine
depending on the outcome recorded in the serial log.
The bit that keeps banging in my head in regards to this is storing it
in the same engine as part of the transaction and so avoiding 2pc.
We discussed this on Drizzle Day, and that was my recommendation.
This would mean, after a transaction has committed, the replication
system asks the engine for a "list of operations" that were performed
by the transaction.
For engines that have this information in their transaction log, it is
a relatively simple task.
Then, in 99.9% of cases when there are not cross engine
transactions, we
never need 2pc.
Although I haven't given this intense deep thought as to various
corner cases...
--
Stewart Smith
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Paul McCullagh
PrimeBase Technologies
www.primebase.org
www.blobstreaming.org
pbxt.blogspot.com
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