On 7/18/13 12:00 PM, Alvaro Herrera wrote:
I think the idea is to have a system in which most of the time the
recovery time will be that for checkpoint_timeout=5, but in those
(hopefully rare) cases where checkpoints take a bit longer, the recovery
time will be that for checkpoint_timeout=6.

I understand the implementation. My point is that if you do that, the fair comparison is to benchmark it against a current system where checkpoint_timeout=6 minutes. That is a) simpler, b) requires no code change, and c) makes the looser standards the server is now settling for transparent to the administrator. Also, my expectation is that it would perform better all of the time, not just during the periods this new behavior kicks in.

Right now we have checkpoint_completion_target as a GUC for controlling what's called the spread of a checkpoint over time. That sometimes goes over, but that's happening against the best attempts of the server to do better.

The first word that comes to mind for for just disregarding the end time is that it's a sloppy checkpoint. There is all sorts of sloppy behavior you might do here, but I've worked under the assumption that ignoring the contract with the administrator was frowned on by this project. If people want this sort of behavior in the server, I'm satisfied my distaste for the idea and the reasoning behind it is clear now.

Greg Smith   2ndQuadrant US    g...@2ndquadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.com

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