On Tuesday 28 August 2007 18:44, Simon Riggs wrote:
> On Tue, 2007-08-28 at 17:59 -0400, Tom Lane wrote:
> > Robert Treat <xzilla@xxxxxxxxxxxxxxxxxxxxx> writes:
> > > Is there some way to force checkpoints on a db doing wal replay?
> >
> > No, it's hardwired to do it when it sees a checkpoint record in the WAL
> > stream.
> >
> > > pg_control last modified: Mon Aug 27 12:12:55 2007
> > > Time of latest checkpoint: Mon Jul 30 19:17:37 2007
> >
> > After looking again at the code, the "last modified" time is the time
> > that a recovery checkpoint was last done, and the "latest checkpoint"
> > is the timestamp of the WAL-stream checkpoint record that triggered it.
> > In a situation where you're catching up on historical WAL they could be
> > far apart, but when a slave is just following the master there shouldn't
> > be a huge difference --- not more than the maximum time to fill a WAL
> > record and ship it over to the slave, for sure.
> >
> > (BTW, I misread it before --- it looks like the "at log time" value
> > printed at startup *is* taken from the checkpoint record that it's
> > trying to roll forward from.)
>
> That's correct. Sorry for not replying earlier; just back from hols.
>
> Jumping back to original thought: Robert, you should be using the last
> checkpoint location, not the last time to decide which xlogs to remove.
>
Looking at last checkpoint location in pg_control, I see:
Latest checkpoint location: 1C/8001E848
How does one translate that into an xlog file name?
--
Robert Treat
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