Re: switch UNLOGGED to LOGGED

On Fri, May 27, 2011 at 10:49:13AM +0100, Leonardo Francalanci wrote:
> > From: Noah Misch <noah(at)leadboat(dot)com>
> > > - the patch is missing the "send all table pages to the
> > > standby" part; is there some code I can use as base?
> >
> > Nothing comes to mind as especially similar.
> >
> > > I guess I have to generate some special log type that
> > > is only "played" by standby servers.
> >
> > What you described in your followup mail seemed reasonable.
>
>
> So, it's ok to have a log item that is replayed only if
>
> WalRcvInProgress()
>
> is true?

No, that checks for WAL streaming in particular. A log-shipping standby needs
the same treatment.

> Is it a correct approach? I couldn't find any other way to
> find out if we are in a standby or a master...

InArchiveRecovery looks like the right thing, but it's currently static to
xlog.c. Perhaps exporting that is the way to go.

> > > - on the standby, the commit part should be played as it
> > > is on the master (that is, removing the INIT fork).
> > > The abort case is different though: it would mean
> > > doing nothing on the master, while removing every forks
> > > but the INIT fork on the standby.
> > > Would it be ok to add to xl_xact_abort a new array of
> > > RelFileNode(s), where for each one at abort all the forks,
> > > except the init fork, have to be deleted by the standby
> > > (while the master shouldn't do anything with them)?
> > > I bet there's a cleaner solution...
> >
> > Your "use less space in xl_xact_commit patch" seems to be going in a good
> > direction here. It would probably also be okay to do a
> >ResetUnloggedRelations()
> > on the standby at every abort of a transaction that had started an UNLOGGED
> ->
> > LOGGED conversion. That is, just a flag might be enough.
>
> ok, but that would mean that a transaction that aborts a conversion
> would try to reset all unlogged relations (traversing all the FS)...
> I don't know if that's acceptable performance-wise.

I'm not sure, either, but I don't figure such operations will be at all common.

nm