Re: Fix checkpoint skip logic on idle systems by tracking LSN progress

On 2016-12-21 16:35:28 -0500, Robert Haas wrote:
> On Wed, Dec 21, 2016 at 4:28 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> > - Similarly I don't like the name "progress LSN" much. What does
> > "progress" really mean in that". Maybe "consistency LSN"?
>
> Whoa. -1 from me for "consistency LSN". Consistency has to with
> whether the cluster has recovered up to the minimum recovery point or
> whatever -- that is -- questions like "am i going to run into torn
> pages?" and "should I expect some heap tuples to maybe be missing
> index tuples, or the other way around?".

That's imo pretty much what progress LSN currently describes. Have there
been any records which are important for durability/consistency and
hence need to be archived and such.

> What I think "progress LSN"
> is getting at -- actually fairly well -- is whether we're getting
> anything *important* done, not whether we are consistent. I don't
> mind changing the name, but not to consistency LSN.

Well, progress could just as well be replay. Or the actual insertion
point. Or up to where we've written out. Or synced out. Or
replicated....

Open to other suggestions - I'm not really happy with consistency LSN,
but definitely unhappy with progress LSN.

Greetings,

Andres Freund