* Jeff Janes (jeff.ja...@gmail.com) wrote: > On Wed, Oct 23, 2013 at 9:20 AM, Stephen Frost <sfr...@snowman.net> wrote: > > * Josh Berkus (j...@agliodbs.com) wrote: > > > On the other hand, it's still true that a high STDDEV indicates a high > > > variance in the response times of a particular query, whereas a low one > > > indicates that most are close to the average. While precision math > > > might not work if we don't have the correct distribution, for gross DBA > > > checks it's still useful. That is, I can answer the question in many > > > cases of: "Does this query have a high average because of outliers, or > > > because it's consisently slow?" by looking at the STDDEV. > > > > The concern is actually the reverse issue- often the question is "is > > this query ever really slow?", or "when is this query really slow?" and > > those questions are not answered by stddev, min, max, nor avg. > > How does max not answer "is this query ever really slow?"?
meh. max can end up being high for about a bazillion reasons and it'd be difficult to really get any understanding of how or why it happened from just that information. > But good point, > if we have a max, then I think a time-stamp for when that max was obtained > would also be very useful. And now we're getting into exactly what I was trying to suggest up-thread: outlier detection and increased logging when a rare event occurs.. Thanks, Stephen
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