Re: [HACKERS] Fix checkpoint skip logic on idle systems by trackingLSN progress

Hi Andres,

On 12/21/16 4:28 PM, Andres Freund wrote:

> Working on committing this (tomorrow morning, not tonight).  There's
> some relatively minor things I want to change:
>
> - I don't like the name XLogSetFlags() - it's completely unclear what
>   that those flags refer to - it could just as well be replay
>   related. XLogSetRecordFlags()?

That sounds a bit more clear.

> - Similarly I don't like the name "progress LSN" much. What does
>   "progress" really mean in that". Maybe "consistency LSN"?

Yes, please.  I think that really cuts to the core of what the patch is 
about.  Progress made perfect sense to me, but consistency is always the 
goal, and what we are saying here is that this is the last xlog record 
that is required to achieve consistency.  Anything that happens to be 
after it is informational only.

> - It's currently required to avoid triggering archive timeouts and
>   checkpoints triggering each other, but I'm nervous marking all xlog
>   switches as unimportant. I think it'd be better to only mark timeout
>   triggered switches as such.

That seems fine to me.  If the system is truly idle that might trigger 
one more xlog switch that is needed, but it seems like a reasonable 
compromise.

-- 
-David
david@pgmasters.net