Re: Add checkpoint and redo LSN to LogCheckpointEnd log message

Greetings,

* Bharath Rupireddy (bharath(dot)rupireddyforpostgres(at)gmail(dot)com) wrote:
> On Fri, Jan 28, 2022 at 11:16 AM Nathan Bossart
> <nathandbossart(at)gmail(dot)com> wrote:
> > I know I voted for "start=%X/%X, end=%X/%X," but looking at this again, I
> > wonder if it could be misleading. "start" is the redo location, and "end"
> > is the location of the checkpoint record, but I could understand why
> > someone might think that "start" is the location of the previous checkpoint
> > record and "end" is the redo location of the new one. I think your
> > original idea of "lsn=%X/%X, redo lsn=%X/%X" could be a good alternative.
> >
> > Іn any case, this patch is small and otherwise looks reasonable to me, so I
> > am going to mark it as ready-for-committer.
>
> Thanks for your review. In summary, we have these options to choose
> checkpoint LSN and last REDO LSN:
>
> 1) "start=%X/%X, end=%X/%X" (ControlFile->checkPointCopy.redo,
> ControlFile->checkPoint)
> 2) "lsn=%X/%X, redo lsn=%X/%X"
> 3) "location=%X/%X, REDO location=%X/%X" -- similar to what
> pg_controldata and pg_control_checkpoint shows currently.
> 4) "location=%X/%X, REDO start location=%X/%X"
>
> I will leave that decision to the committer.

I'd also vote for #2. Regarding 3 and 4, I'd argue that those should
have been changed when we changed a number of other things from the
generic 'location' to be 'lsn' in system views and functions, and
therefore we should go change those to also specify 'lsn' rather than
just saying 'location'.

Thanks,

Stephen