me@xxxxxxxxxxxxxxxx (Benjamin Arai) writes: > If you are looking for a SoC idea, I have listed a couple below. I > am not sure how good of an idea they are but I have ran into the > following limitations and probably other people have as well in the > past. Actually, I have a thought on a SoC idea... The general notion would be to try to come up with some more rational information on setting the default column statistics width. http://www.postgresql.org/docs/8.2/interactive/runtime-config-query.html#GUC-DEFAULT-STATISTICS-TARGET http://www.postgresql.org/docs/8.2/interactive/planner-stats.html Now, the default value has long been 10. There are cases where people find they need to set it higher; that has always been pretty trial-and-error. My suspicion is that: a) The default should probably be a bit higher than 10 b) Some analysis of stats and schema on an individual table could perhaps provide more specific values for specific columns. - Data type might provide guidance; there's little need for >3 values on a binary column, for instance. - If there is a NOT NULL UNIQUE constraint on a column, that might suggest > 10 values - If the column is known to have 150 unique values, that might suggest SET STATISTICS 150 It might be worth looking at the *least* frequently occuring values, and set stats high enough to make it likely that at least one such value would be pulled in... - Some kinds of values (dates, floats) are sorta continuous in value; having 10 bins may be pretty OK for such There are probably some other heuristics to be had; this is just some ideas off the top of my head. Nobody has gone through any sort of real analysis of this; there likely is merit to doing so... -- let name="cbbrowne" and tld="cbbrowne.com" in name ^ "@" ^ tld;; http://cbbrowne.com/info/finances.html Where do you *not* want to go today? "Confutatis maledictis, flammis acribus addictis" (<http://www.hex.net/~cbbrowne/msprobs.html>
