On 10/03/2014 09:42 PM, Bruce Momjian wrote:
On Fri, Oct 3, 2014 at 03:30:35PM -0300, Arthur Silva wrote:> Every GUC add complexity to the system because people have to understand > it to know if they should tune it. No GUC is zero-cost.Please see my blog post about the cost of adding GUCs: http://momjian.us/main/blogs/pgblog/2009.html#January_10_2009 That's true Bruce (nice post, it was a good reading). But how can we ignore 25%+ improvements (from 8 to 24)? At very least we should delivery some pretty good defaults.Well, checkpoint_segments was a similar case where we couldn't give good tuning advice so we went with a server log file warning if it needed to be increased --- this might be a similar case.
I have no idea how to decide at runtime whether it should be increased or not. If that was feasible, we probably could make it tune itself on the fly - it's not like checkpoint_segments where you need more disk space if you increase it.
I stand by my decision to make it a #define, at least until someone voices their objection in the form of a documentation patch.
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