Re: SSI atomic commit

On Thu, Jul 07, 2011 at 04:48:55PM -0400, Tom Lane wrote:
> Seems to me there's a more fundamental reason not to do that, which is
> that once you've done PREPARE it is no longer legitimate to decide to
> roll back the transaction to get out of a "dangerous" structure --- ie,
> you have to target one of the other xacts involved instead.  Shouldn't
> the assignment of a prepareSeqNo correspond to the point where the xact
> is no longer a target for SSI rollback?

That part is already accomplished by setting SXACT_FLAG_PREPARED (and
choosing a new victim if we think we want to abort a transaction with
that flag set).

prepareSeqNo is being used as a lower bound on the transaction's commit
sequence number. It's currently set at the same time as the PREPARED
flag, but it doesn't have to be.

Dan

-- 
Dan R. K. Ports              MIT CSAIL                http://drkp.net/