Re: [HACKERS] Restartable Recovery

Nice.  I was going to ask if this could make it into 8.2.

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Simon Riggs wrote:
> On Sun, 2006-07-16 at 20:56 +0100, Simon Riggs wrote:
> > On Sun, 2006-07-16 at 15:33 -0400, Tom Lane wrote:
> > > Simon Riggs <simon@2ndquadrant.com> writes:
> > > > On Sun, 2006-07-16 at 12:40 -0400, Tom Lane wrote:
> > > >> A compromise that might be good enough is to add an rmgr routine defined
> > > >> as "bool is_idle(void)" that tests whether the rmgr has any open state
> > > >> to worry about.  Then, recovery checkpoints are done only if all rmgrs
> > > >> say they are idle.
> > >
> > > > Perhaps that should be extended to say whether there are any
> > > > non-idempotent changes made in the last checkpoint period. That might
> > > > cover a wider set of potential actions.
> > >
> > > Perhaps best to call it safe_to_checkpoint(), and not pre-judge what
> > > reasons the rmgr might have for not wanting to restart here.
> >
> > You read my mind.
> >
> > > If we are only going to do a recovery checkpoint at every Nth checkpoint
> > > record, then occasionally having to skip one seems no big problem ---
> > > just do it at the first subsequent record that is safe.
> >
> > Got it.
>
> I've implemented this for BTree, GIN, GIST using an additional rmgr
> function     bool rm_safe_restartpoint(void)
>
> The functions are actually trivial, assuming I've understood this and
> how GIST and GIN work for their xlogging.
>
> "Recovery checkpoints" are now renamed "restartpoints" to avoid
> confusion with checkpoints. So checkpoints occur during normal
> processing (only) and restartpoints occur during recovery (only).
>
> Updated patch enclosed, which I believe has no conflicts with the other
> patches on xlog.c just submitted.
>
> Much additional testing required, but the underlying concepts are very
> simple really. Andreas: any further gotchas? :-)
>
> --
>   Simon Riggs
>   EnterpriseDB          http://www.enterprisedb.com

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  Bruce Momjian   bruce@momjian.us
  EnterpriseDB    http://www.enterprisedb.com

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