Re: Speedup twophase transactions

>
> + *      * RecoverPreparedTransactions(), StandbyRecoverPreparedTransact
> ions()
> + *        and PrescanPreparedTransactions() have been modified to go
> throug
> + *        gxact->inredo entries that have not made to disk yet.
>
> It seems to me that there should be an initial scan of pg_twophase at
> the beginning of recovery, discarding on the way with a WARNING
> entries that are older than the checkpoint redo horizon. This should
> fill in shmem entries using something close to PrepareRedoAdd(), and
> mark those entries as inredo. Then, at the end of recovery,
> PrescanPreparedTransactions does not need to look at the entries in
> pg_twophase. And that's the case as well of
> RecoverPreparedTransaction(). I think that you could get the patch
> much simplified this way, as any 2PC data can be fetched directly from
> WAL segments and there is no need to rely on scans of pg_twophase,
> this is replaced by scans of entries in TwoPhaseState.
>
>
I don't think this will work. We cannot replace pg_twophase with shmem
entries + WAL pointers. This is because we cannot expect to have WAL
entries around for long running prepared queries which survive across
checkpoints.

Regards,
Nikhils