On Jul 10, 2011, at 6:10 PM, Lee, David wrote: > I'm experimenting with Range Indexes over dateTime and dayTimeDuration values. > I have a large number (millions) of small documents/fragments each with a > dateTime and/or dayTimeDuration. > > Currently these are in millisecond accuracy. For most things I dont need the > ms accuracy but its useful on occasion. I am wondering is there a > detrimental effect of this precision ?
I've never empirically tested these things, but since you didn't get another answer, I'll jump in. If you're storing as dateTime or dayTimeDuration I doubt you'll see a worthwhile advantage in speed or memory by rounding to seconds. > However if I truncate the dateTime to seconds then there will be vastly fewer > unique values . > > I am curious what the effect, if any, would be of doing this. Does the size > or search time of the range indexes depend on the number of unique values ? > or more on the number of fragments ? Number of fragments * number of values per fragment. > I am thinking it would have to depend on both as it needs to map value -> > (set of fragments). > So what is the difference if the common case is nearly 1:1 value:fragment vs > 1:many value: fragment ? Think of it as an array of structs, each entry an id and value. Each has a fixed size in memory. -jh-
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