"Greg Sabino Mullane" <[EMAIL PROTECTED]> writes:
N.B. My own personal starting default is 2, but I thought 3 was a nice middle ground more likely to reach consensus here. :)
Your argument seems to be "this produces nice results for me", not "I have done experiments to measure the actual value of the parameter and it is X". I *have* done experiments of that sort, which is where the default of 4 came from. I remain of the opinion that reducing random_page_cost is a band-aid that compensates (but only partially) for problems elsewhere. We can see that it's not a real fix from the not-infrequent report that people have to reduce random_page_cost below 1.0 to get results anywhere near local reality. That doesn't say that the parameter value is wrong, it says that the model it's feeding into is wrong.
I would like to second that. A while back I performed a number of experiments on differing hardware and came to the conclusion that *real* random_page_cost was often higher than 4 (like 10-15 for multi-disk raid systems).
However I have frequently adjusted Pg's random_page_cost to be less than 4 - if it helped queries perform better.
So yes, it looks like the model is the issue - not the value of the parameter!
regards
Mark
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